new method to parse header info, shorten GitHub Plugin URI header to owner/repo

Added a new method to parse the GitHub Plugin headers. This should enable an easier transition to the possibility of other repos. Also, shortened the GitHub Plugin URI to only need owner/repo, but allow for full URI if provided.
greatly simplified the return of $git_repo array and other fixes as suggested by @GaryJones
comment on parse_url
Merge pull request #17 from afragen/feature/short-uri

Feature/short uri
remove variable for GitHub domain, placed all array declarations of header info into appropriate switch case statements for consistency.
too many spaces
add short URI for themes
version updates, bring README and CHANGES in line.
Merge branch 'refs/heads/develop'