Add basic support for modes: none, new_episodes, once
Clean up new mode configuration phpdoc
Update wording in phpdoc and exception
phpdoc updates for supported modes
Improved 'once' mode support
Add mode validation
Create Storage parent class
Add tests
Moves common storage logic to AbstractStorage class.
Fixes typo.
Merge pull request #72 from php-vcr/request_blocking_support

Request blocking support