Fully implement structures

[iddm]

Some fields of structures are not implelemented due to the lack of information on the api.challonge.com web-site or due to the lack of time :)

Tournament:
    // category: ??,
    // <signup-cap nil="true"/>
    // <start-at nil="true"/>    
    // <started-checking-in-at nil="true"/>
    // <state>underway</state>

    // <tie-breaks type="array">
    // <tie-break>match wins vs tied</tie-break>
    // <tie-break>game wins</tie-break>
    // <tie-break>points scored</tie-break>
    // </tie-breaks>

    // <subdomain nil="true"/>
    // <sign-up-url nil="true"/>

Match:
    // attachment_count: ,
    // group_id: ,
    // location: 
    // scheduled_time:
    // underway_at: