Used python traceback module to set name of theano.function to file_name:line_number.
Made default name functionality more robust to the existane of modules.
Integrated suggestions from other developers.
Made robust to stack manipulations and added test.
Simplified code. It no longer handles stack manipulations but will be marginally faster.
Merge pull request #1981 from daemonmaker/function_name

Used traceback module to set name of theano.function to file_name:line_number.