TAJO-1272: Change snapshot version from 0.9.1 to 0.10.

Closes #323
Add more documents and reflect a Hyunsik's comment
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into index_support
Merge branch 'index_support' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-838_3