Add example for issue number

Technically, anything in the third argument is passes as a string, so you can look at any file if you know the hash (for instance, `blob/HASH/app/index.js`. However, having the issue number passed seems to me to be something really useful to my workflow, so I was hoping to find something in the documentation about it. 

Another possibility would be to enable a fourth argument for issue number. I'm happy to do a PR for this if something things it might be of more worth than just this edit.

[doc] Readme: use text from hub man page for hub.protocol.

Fix wrong URL of current user for GHE

- "git protocol for read and ssh for write" had introduced
  additional expectations of behavior.

GHE is using /api/v3 as the path prefix for all API URLs. There’s one miss case when getting current user.

This is to fix https://github.com/github/hub/issues/660#issuecomment-60757883

Fix broken colorized verbose output

From https://github.com/github/hub/issues/660#issuecomment-60757883, the colorized verbose output is broken. The old implementation tries to use ‘\e’ which is not recognized in a Go string. Let’s Use ‘\033’ instead.

Pull back man page rake task from https://github.com/github/hub/blob/1.12-stable

[trivial] typo 'isPriavte' should be 'isPrivate'.

Improve `hub alias` support for csh and tcsh.

Delegate `git —-version` and `git —-help` to Hub

Fix Windows build

Use github.com/mattn/go-isatty to check terminal

Due to weirdness in my local copy/environment (FreeBSD), attempts to run the
test suite have met with stiff resistance--cucumber reports that git doesn't
exist (!), and /script/test gets confused over core.editor and then bombs
talking about file desciptors.  However, the alias tests in cucumber seem to
pass.

These shells don't support $() notation, so fall back to `` notation.

In these shells, the correct invocation is `alias git hub`, not `alias
git=hub`.

This just adds tcsh to the list of supported shells, with its profile as
~/.tcshrc.

Bump to Go 1.3.3 in Travis

Add instruction to install `hub` 2.x from Homebrew README

Updated Homebrew recipe has been merged:
https://github.com/Homebrew/homebrew/commit/a746c26f8a7a6dd64850ba2cb9e76363bfca41e0

Update README for 2.x release

Typo in build script to disable update

Also fix a output typo in autoupdate which is never runs

Revert to @mislav's solution to get base branch for pull request

As discussed https://github.com/github/hub/pull/646/files#r19065050,
we'd need to defend against getting base branch and tracking branch when
generating diff.

Bump version to 2.2.0-preview1 for release

Clean up project.go

* Clean up unused methods
* Refactor to Project.Remote

Fix git commit summary in pull request message template