Fixes #426 , #418

Fixes #419

It's the same as the vimscript type, but shorter and more obvious.

Fixes #415

Fixes #381

Use a `ps:` (powershell) command to copy the completions file so that we
can use directory globbing to find the file.

Fixes #1

Fixes #407

This reverts commit d570f781.

This was reverted because it's blocking a 0.5.0 release. Windows is
foreign to me, and apparently globs are not allowed.

See:
https://ci.appveyor.com/project/BurntSushi/ripgrep/build/1.0.341/job/7o1jqicmtwm7oa00

Previously, `get_matches` would return even if --help or --version was
given, and we could check for them manually. That behavior seems to have
changed. Instead, we must use get_matches_safe to inspect the error to
determine what happened.

We can't use the same process for -V/--version since clap will
unconditionally print its own version info. Instead, we rename (internally)
the version flag so that clap doesn't interfere.

This permits setting the maximum line width with respect to the number
of bytes in a line. Omitted lines (whether part of a match, replacement
or context) are replaced with a message stating that the line was
elided.

Fixes #129

Fixes #345.

Fixes #340

This changes the default behavior of ripgrep to *not* show line numbers
when it is printing to a tty and is only searching stdin.

Fixes #380

[breaking-change]

It's not clear what exactly is happening here, but the Read implementation
for text decoding appears a bit sensitive. Small pertubations in the code
appear to have a nearly 100% impact on the overall speed of ripgrep when
searching UTF-16 files.

I haven't had the time to examine the generated code in detail, but
`perf stat` seems to think that the instruction cache is performing a lot
worse when the code slows down. This might mean that excessive inlining
causes a different code structure that leads to less-than-optimal icache
usage, but it's at best a guess.

Explicitly disabling the inline for the cold path seems to help the
optimizer figure out the right thing.

This includes, but is not limited to, UTF-16, latin-1, GBK, EUC-JP and
Shift_JIS. (Courtesy of the `encoding_rs` crate.)

Specifically, this feature enables ripgrep to search files that are
encoded in an encoding other than UTF-8. The list of available encodings
is tied directly to what the `encoding_rs` crate supports, which is in
turn tied to the Encoding Standard. The full list of available encodings
can be found here: https://encoding.spec.whatwg.org/#concept-encoding-get

This pull request also introduces the notion that text encodings can be
automatically detected on a best effort basis. Currently, the only
support for this is checking for a UTF-16 bom. In all other cases, a
text encoding of `auto` (the default) implies a UTF-8 or ASCII
compatible source encoding. When a text encoding is otherwise specified,
it is unconditionally used for all files searched.

Since ripgrep's regex engine is fundamentally built on top of UTF-8,
this feature works by transcoding the files to be searched from their
source encoding to UTF-8. This transcoding only happens when:

1. `auto` is specified and a non-UTF-8 encoding is detected.
2. A specific encoding is given by end users (including UTF-8).

When transcoding occurs, errors are handled by automatically inserting
the Unicode replacement character. In this case, ripgrep's output is
guaranteed to be valid UTF-8 (excluding non-UTF-8 file paths, if they
are printed).

In all other cases, the source text is searched directly, which implies
an assumption that it is at least ASCII compatible, but where UTF-8 is
most useful. In this scenario, encoding errors are not detected. In this
case, ripgrep's output will match the input exactly, byte-for-byte.

This design may not be optimal in all cases, but it has some advantages:

1. In the happy path ("UTF-8 everywhere") remains happy. I have not been
   able to witness any performance regressions.
2. In the non-UTF-8 path, implementation complexity is kept relatively
   low. The cost here is transcoding itself. A potentially superior
   implementation might build decoding of any encoding into the regex
   engine itself. In particular, the fundamental problem with
   transcoding everything first is that literal optimizations are nearly
   negated.

Future work should entail improving the user experience. For example, we
might want to auto-detect more text encodings. A more elaborate UX
experience might permit end users to specify multiple text encodings,
although this seems hard to pull off in an ergonomic way.

Fixes #1

Fixes #381

We add scss to the existing `css` file type and `ejs` to the existing
`html` file type.

Fixes #393

(This is what I get for directly pushing to master.)

When writing paths like `!/foo` in gitignore files (or when using the
-g/--glob flag), the presence of `!` would prevent the gitignore builder
from noticing the leading slash, which causes absolute path matching to
fail.

Fixes #405

Tested with local cargo build paths.

Also document that ctrl-c doesn't restore the termcolor.
Fixes #347.