Issue #282 Created ReleaseAsset, ReleaseAssets interfaces
Issue #282 Created RtReleaseAsset, RtReleaseAssets,
RtReleaseAssetITCase, RtReleaseAssetTest
Issue #282 Created MkReleaseAsset and MkReleaseAssets classes
Issue #282 Created RtReleaseTest, RtReleaseAssetsTest,
RtReleaseAssetsITCase. Moved release asset-related tests and puzzles
from RtReleaseTest to RtReleaseAssetsTest.
Issue #282 Implemented RtReleaseAssets.upload()
Merge branch 'master' into 282

Conflicts:
	src/test/java/com/jcabi/github/RtReleaseTest.java
Merge pull request #442 from carlosmiranda/282

Issue #282 Implemented Release Asset Uploads