* Commands now completely manages 'help', so that 'help' returns full command list/doco and 'help cmd' returns doc for just that command
* Turned out.session_start() and out.session_end() into hook methods: Pry.hooks :before_session, and :after_session
* Refactored Pry#initialize, so no longer individually setting accessors and hash options, instead using ConfigOptions to iterate over accessors and set their default value to Pry.send(accessor_name)
* TO DO: rewrite tests in terms of new program structure, since they're all failing due to major change (not because functionality is lacking but due to assumptions tests were making about program structure)
