Add parser tests
Add BlazeParser for scalar expressions
Move ScalarSymbol to parser
Give z a reasonable type
Add failing chained comparison test
Move exprify to parser.py
Add test for string comparison
Test string comparison with isidentical
Use literals where possible
Remove empty line
Break out test into a class and add unary sub test
Implement UnaryOp parsing
Python 2.6 raises SyntaxError because dict/set comps are not in the grammar
sys import
Force Python 3 to evaluate unary operators as core types
Add scope check for overlapping names
Use raises from compatibility
Change names to match ast node names
Test simple comparisons and floordiv
Remove unused code