Support `callback_uri` for /oauth/token API call.
Merge pull request #15 from kevinjqiu/support-callback-uri-for-token-request

Support `callback_uri` for /oauth/token API call.
Update CHANGELOG.md
Update CHANGELOG.md
Updated version number
Raise exception instead of WePayError exception
Update CHANGELOG.md
WePayError handling; update SDK version to 0.2.4
Merge pull request #16 from aroundthesea/master

Revert WePayError handling
Raise Exception; updated version to 0.3.0 to reflect breaking change
Merge pull request #17 from aroundthesea/master

Raise Exception; updated version to 0.3.0 to reflect breaking change
Update CHANGELOG.md