reworking CONTRIBUTING to be more than bullet points
add some new sections

expanded on "How is the codebase organised?" and "What needs to be done?"
added notes about integration tests
moved project structure notes in
removed project structure, moved contributing up
dropped 'submitting an issue' section
added deployment doc
removed deployment section
word wrapping
added git push command
Merge pull request #390 from forki/Build

Using FAKE 2.10
Support to Create Gists
Remove need for NewGistFile.cs
Initialize Files

Initialize Files to reduce needless setup to create a gist.
Remove suppress attribute
Delete Gist

Add ability to delete gist with test cases.
Complete Gist API
Passing tests and fix build for MonoAndroid and MonoTouch
Add Octokit PCL and all relevant plumbing

Add Octokit-PCL and ConcurrentCache which is used by the PCL in lieu of
the ConcurrentDictionary, which is not available on Windows Phone 8.
Fix convention tests running for gists