.gitignore: Ignore all Gemfiles except for the main Gemfile

This change allows for local Gemfiles to exist for development purposes
without contaminating the gemspec with other dependencies.
MapStart: Exclude CRC information from LOG_REGEX

Extra properties are already captured by the parser, rendering the CRC
match superfluous and resulting in a duplicate property in MapStart
events.
PlayerKill: Capitalize class name in documentation
Game: Move event filter declarations into a self-contained module

Create module EventFilters, designed to be included by any object that
contains a collection of Events. EventFilters contains a series of
declarations that can be used as shortcuts for returning only Events of
a given subclass.
Australium: Force encoding to UTF-8

For strings to be properly handled and stored into databases, all data
is forced into UTF-8 for now. In future we may explore other
alternatives to preserve encoding without causing unnecessary amounts
of database configuration.
Parser: Increase parsing efficiency; add attributes

This commit introduces two new attributes, game_id and line_number, to
generated Event objects. Between the game_id, a unique hash of all the
game's lines, and the line_number, the position of each Event in the
game log, all events can be uniquely identified. This change is
necessary for database storage and retrieval to be possible.
Add optional database event caching

By requiring 'australium/event_cache' in addition to the gem itself,
Australium is now capable of storage, retrieval, and arbitrary queries
of Events contained within a Sequel database.

EventCache#query responds to the same methods as Sequel::Database, but
will turn the resulting Sequel::Dataset into an array of Events. If the
Sequel::Dataset cannot be directly turned back into Event objects, an
exception will be thrown.

Note: GameState objects are currently not preserved by database
caching, as they are not yet efficient enough to store.
Australium v1.1.0