Bot player for Player Two

Computer will make a move after waiting 400ms. Implementation is meh.

* breaks existing specs :cry:
    * Need `$timeout.apply()` in specs
    * `thinking` flag to prevent human interaction during bot's turn breaks test
* strategy pattern in `SuggestionService` is sound, but there's an obscene amount of list comprehensions

The bot is kinda dumb. It's strategy is:

1. block opponent's winning move
2. mark a random empty square

* [ ] play (decently) against the user
    * [ ] complete an existing winning move
    * [x] block human opponent if they're about to win
    * [x] mark a random, empty square
* [x] prevent human from playing during computer's turn
* [ ] fix specs
* [ ] coverage that `GameController` uses `SuggestionService`
* [ ] coverage that computer *thinks* for a period of time; prevents human player from playing