Allow qualified column names w/ aggregate functions

I bumped into a problem when attempting to generate something like COUNT('tablename'.'column').
Add prototype to change schema name
Merge pull request #129 from janstice/patch-1

Allow qualified column names w/ aggregate functions
test for schema with aggregation
Merge pull request #131 from yc662/addTest

test for schema with aggregation
Merge pull request #130 from shernshiou/change_schema

Ability to change schema name