Updated the base URI for the China region
Updated the base URI for the China region

Updated the base URI for the China region from https://cn.api.blizzard.com to https://gateway.battlenet.com.cn.  This matches the current documentation at https://develop.battle.net/documentation/guides/regionality-and-apis.  Also changed the base URI for OAuth for China per the documentation at https://develop.battle.net/documentation/guides/using-oauth.  Resolves #71.
danjagnow/ArgentPonyWarcraftClient