create twitter.py
OAuth 1.0 example partially added.
OAuth 1.0 example completed authorization chain.
Write interface ApiBase. GithubApi and SlackApi implements it.
Refactor static *_api_call() into self._api_call().
Merge oauth-1.0a twitter example into develop
Gmail api example added.
Fix favicon problem.
Implement Gmail OAuth 2.0.
GithubApi.oauth_callback() fetches its username.
Complete IMAP example.
GmailApi fetches user email.
Fully implement GmailApi.
Merge branch 'gmail-api' into develop
Restructure api clients' and add GmailApi.