fixes to finally get StartAuth() to work end-to-end
StartAuth(0 works, moving into Callback() handling
Savings before changes for Twitter OAuth1
fighting Twitter's vs Go's encoding for signature generation
twitter StartAuth() now working
OAuth2 code exchange for token done
refactoring Authorizers and added AuthConfig validation
continued work on refactoring authorizer interfaces
finalized general refactoring of OAuth2 providers, needs testing
refactor postRequestForJson; work on OAuth for Twitter
bugfix to Twitter provider
Merge branch 'dev'