Update README.md

Although the cinst alias will still function (for now anyway), the recommend installation command for a Chocolatey package is the slightly more descriptive ```choco install GitLink``` command, as you can see here:

http://chocolatey.org/packages/githublink
Merge pull request #23 from gep13/patch-1

Update README.md
Added note for rename action
Renamed image in doc
Updated test cases
Added docs for integration tests
Small update
Added first integration tests for GitHub
Added integration tests for GitHub and BitBucket
Added support for multiple hosting providers and implemented the BitBucket provider.
Fixed unit test and updated comments