added a installation.md doc based on http://apigility.org/documentation/install
Merge pull request #1 from unixmen/master

added a installation.md doc based on http://apigility.org/documentation/...
[#1] repo organization

- Created "intro" section to documentation, and moved installation documentation
  into it.
- Created a table of contents, linking to the installation documentation
Merge branch 'hotfix/1'

Close #1