Add a minimal readme and fix link in license

[av skip]

Author: tkelman

LICENSE.md

@@ -1,7 +1,7 @@
 > Copyright (c) 2009-2016: Jeff Bezanson, Stefan Karpinski, Viral B. Shah,
 > and other contributors:
 >
-> https://github.com/JuliaLang/julia/contributors
+> https://github.com/JuliaPackaging/Git.jl/contributors
 >
 > Permission is hereby granted, free of charge, to any person obtaining
 > a copy of this software and associated documentation files (the

README.md

@@ -6,4 +6,12 @@
 
 Julia wrapper for command line Git
 
+This package provides Julia wrappers for some common Git operations,
+as used by the Julia package manager in versions 0.4 and earlier.
+
+If you do not already have `git` installed and on your system `PATH`, then
+adding this package (or running `Pkg.build("Git")` will download a local binary
+copy of command-line git if you are using Windows, Mac OS X via
+[Homebrew.jl](https://github.com/JuliaLang/Homebrew.jl), or Linux on x86/amd64 architectures.
+
 [![Git Badge](http://forthebadge.com/images/badges/uses-git.svg)](http://forthebadge.com)