README: add up some marketing

Author: ethomson

README.md

@@ -6,8 +6,20 @@ libgit2 - the Git linkable library
 [![Coverity Scan Build Status](https://scan.coverity.com/projects/639/badge.svg)](https://scan.coverity.com/projects/639)
 
 `libgit2` is a portable, pure C implementation of the Git core methods
-provided as a re-entrant linkable library with a solid API, allowing you to
-write native speed custom Git applications in any language with bindings.
+provided as a linkable library with a solid API, allowing to build Git
+functionality into your application.  Language bindings like
+[Rugged](https://github.com/libgit2/rugged) (Ruby),
+[LibGit2Sharp](https://github.com/libgit2/libgit2sharp) (.NET),
+[pygit2](http://www.pygit2.org/) (Python) and
+[NodeGit](http://nodegit.org) (Node) allow you to build Git tooling
+in your favorite language.
+
+`libgit2` is used to power Git GUI clients like
+[GitKraken](https://gitkraken.com/) and [gmaster](https://gmaster.io/)
+and on Git hosting providers like [GitHub](https://github.com/),
+[GitLab](https://gitlab.com/) and
+[Visual Studio Team Services](https://visualstudio.com/team-services/).
+We perform the merge every time you click "merge pull request".
 
 `libgit2` is licensed under a **very permissive license** (GPLv2 with a special
 Linking Exception).  This basically means that you can link it (unmodified)