WIP beginning of Match endpoint

Created all the datatypes
Added match lookup method

Created a method to do match lookups in the Riot API. The API limits
only one match lookup and it is optional to download the entire
timeline of events.

Tests have been added as well.
Merge branch 'upstream-master' into match2.2

Merge all changes from TrevorSStone\goriot into match2.2
Slight changes for readability

Renamed the spell fields in `Participant` to match item fields
in `ParticipantStats`.

Moved the `matchID` to be the last argument in the event that
Riot allows searching for more than one in the future.
WIP Match history

Added a new data structure and fixed a reference to the wrong one
in `ParticipantIdentity`. The lookup method for isn't complete yet.

TODO:

* more tests
* expand number of champions allowed (arbitrary limit of 40)
* more clear way of creating comma seperated strings
Using a new way of creating url parameter strings

After discussing with @TrevorSStone on how best to proceed in #36,
I decided to go with two separate functions for creating parameter
strings. One is focussed on joining a `[]string` and the other
converts a `[]int64` to `[]string` and then joins. This is hidden
behind custom types and a `String()` interface.

I've used this function only in MatchHistory so far but the goal
is to eventually spread it to the other endpoints.
Updated tests for Match History
Merge pull request #35 from mattcan/match2.2

Match2.2 API