Merge branch 'release/v0.0.7' into develop
-Added all method for relation version
-Basic implementation supporting aggregation methods in relation
-Added QueryMethods constant
-Remove including Enumerable module in QueryIterator
-Moving aggregation methods calling to relation
-Just in place executing query for aggregation functions
Merge branch 'feature/single_value_chainer' into develop
-Bump version to 0.0.8
-Fixed gem description
Merge branch 'release/v0.0.8'