changed all instances of "Github" to "GitHub"

"GitHub" is the proper name of the site. It should either only be referred to as "github.com" when in a URL (including git) or as "GitHub" (the proper name). 

It should never be referred to as "Github".
Merge pull request #14 from garrett/patch-1

changed all instances of "Github" to "GitHub"
Fix typos.
Merge pull request #15 from jrafanie/fix_typos

Fix typos.
Added Current Sprint doc
Merge pull request #16 from chessbyte/current_sprint

Added Current Sprint doc
Added Current Sprint to Readme
Merge pull request #17 from chessbyte/add_current_sprint_to_readme

Added Current Sprint to Readme
Adding Documentation for Enabling External Authentication

Adding ManageIQ/Guides for installing and enabling
external authentication via IPA.
PR Review Changes to the External Authentication Guide.