Change the kudo checking logic in the Meeting model.

Fixed the logic for Meeting#can_give_kudo?, to better match the state of whether the user has given a kudo to any of the meeting's topics.

Removed the time checking code in Meeting#kudos_available?, as well as the entire Meeting#kudos_period_open? method.

Removed Time setting in the meeting_spec examples around kudo checking.

Refactored the examples around Meeting#can_give_kudo? to be properly isolated from the database.
Clean up kudo checking logic in Topic model.

Replaced Topic#can_add_kudo? with Topic#given_kudo?, which no longer checks the state of the parent Meeting record.

Flipped the guard logic on Topic#give_kudo_as, to match the logic change in #can_add_kudo?

Extracted #kudo_given_error private method, to better separate the error return code.

Modified the Topic model examples to match the new methods and logic changes.
Modify Meeting decorator to match changed kudo methods.

Removed the Time.current argument from the calls to #kudos_available?.

Changed the examples to set the Meeting#kudos_open? flag, rather than set a known time.
Remove current time from ApplicationHelper#kudos_prompt.

Stopped setting the current time in the kudos-related examples in spec/features/user/view_meeting_spec.
Merge pull request #30 from LasVegasRubyGroup/meeting_kudos_refactor

Meeting kudos refactor
rename Meeting#can_give_kudo? to given_kudo? - since it does not actually check whether they can currently give a kudo (which depends on whether open_kudos! has been run), and to make it parallel to Topic#given_kudo?