Merge pull request #5 from dazinator/master

Added indexer to help address jehugaleahsa/SQLGeneration#4
Treat functions as filters

In the case that a function can return true or false, it makes sense to
handle it as a WHERE clause filter. An example would be the CONTAINS
function from T-SQL.
Merge pull request #1 from jehugaleahsa/master

I am pulling this functionality into my own fork..