This makes exa work on other platforms than linux and macosx.

This fixes a bug where an extra header line was printed when in --long --grid mode.

This commit removes the threadpool in `main.rs` that stats each command-line argument separately, and replaces it with a *scoped* threadpool in `options/details.rs` that builds the table in parallel! Running this on my machine halves the execution time when tree-ing my entire home directory (which isn't exactly a common occurrence, but it's the only way to give exa a large running time)

The statting will be added back in parallel at a later stage. This was facilitated by the previous changes to recursion that made it easier to deal with.

There's a lot of large sweeping architectural changes. Here's a smattering of them:

- In `main.rs`, the files are now passed around as vectors of files rather than array slices of files. This is because `File`s aren't `Clone`, and the `Vec` is necessary to give away ownership of the files at the appropriate point.
- In the details view, files are now sorted *all* the time, rather than obeying the command-line order. As they're run in parallel, they have no guaranteed order anyway, so we *have* to sort them again. (I'm not sure if this should be the intended behaviour or not!) This means that the `Details` struct has to have the filter *all* the time, not only while recursing, so it's been moved out of the `recurse` field.
- We use `scoped_threadpool` over `threadpool`, a recent addition. It's only safely used on Nightly, which we're using anyway, so that's OK!
- Removed a bunch of out-of-date comments.

This also fixes #77, mainly by accident :)

Fixes #71 - the I/O error should now be displayed as an error, rather than as a panic.

Also, fix some comments.

Had to thread the value in at display-time to get it to only query the attributes once!

This isn't the nicest way to do it, but this *is* a bit of an edge-case (it's the only thing where a column depends on something that gets calculated later)

This prints three separate groups of child nodes: firstly the xattrs, then the errors, then any file children. It's done this way to only check for the 'last' child when necessary.

This does a similar thing that we did with the xattrs, except with the nested files: it removes the 'this' field on File, and replaces it with a method (to_dir) that has the same effect.

This means we get to remove a bunch of 'recurse' fields and parameters that really had no business being there! Now the table doesn't need to know whether it's going to need to list files recursively or not.

This changes the way extended attributes (xattrs) are printed. Before, they were artificially printed out on their own line both in lines mode *and* details mode, which looked a bit weird. Now, they are additional 'child nodes' of that item that get printed alongside errors.

All this allows all the 'extra info' that is going to be present for very few entries to be consolidated and listed in the same way, without resorting to extra printlns.

As a great side-effect, it allows taking out some of the more redundant code in the Table impl -- it is now *always* going to be in create-child-nodes mode, as *any* file now can, not only when we have the --tree flag in use.

Also, it now actually displays errors when failing to read the extended attributes, such as if the user doesn't have permission to read them.

The extended attribute flag has been temporarily disabled while I work out the best way to do it!

Now we have one Ur-module that contains functionality common to both supported platforms.

The benefits of doing it this way are that:

1. It doesn't implement a dummy interface - rather, there will be less code generated when the feature is not present;
2. The code shared between them can be kept in sync. The other two modules were something like 80% the same.

Have to collect the results into a Vec in order to make sure we only do the ending part for the last one.

When tree mode is active, this will print out errors as another form of child node in the tree, instead of in one big block before any output.

The 'this' field now holds the io::Result of the readdir call, rather than only a *successful* result.

This will be used to not provide any information for the rows that will have no data (attributes, errors).

This is part of work to make the flow of files more iterator-able, rather than going in and out of vectors. Here, a Dir returns an iterator of files, rather than a pre-filled vector.

For now, this removes the ability for error messages to be displayed. Will be added in later though!

This is very slow (see #28) at the moment, so there's an option to switch off repo discovery. However, they were still always being queried. Now, if there's no Git option in the flags, it won't try to discover a repo.

This kind of abuses the details view by giving it no columns when the Columns value is None (it's now Optional).

Fixes #74. There's one argument for changing the arrow, and none against!

These replace `init()` and `tail()` which are deprecated in favour of these.

In fact, it's a good thing they're deprecated, because part of the path_prefix code involved working around a call to init() that would panic otherwise - doing the same check with an `Option` is much more ergonomic.

Use the "install" program to install

The separator_width field in the term_grid crate was replaced with a filling field.

updates libgit2 to build on latest nightly