Parse: Add NOTE to DRY GenidPattern/GenidExpression.
Change new to simple_expr
Parser test: Add regression test for #41
Parser: Add precedence tests for int and float arithmetic
Parser: Ensure p_error arg is instance of ast.Node before processing
Parser test: Complete precedence tests
Parse: p_error takes a token as a parameter
Parser test: Move method after the helper functions it uses
Parser test: Remove duplicate tests
AST: Add sub-Expression nodes to __repr__ for debuggability
Parser test: _assert_(non)?_equivalent can now take expr lists as args
Parser test: Refactoring

* Split precedence and associativity tests to several test functions
* Use new _assert_equivalence methods that accept lists directly
* Introduce some associativity tests for:
  * Float
  * Bool
  * mod
  * power
* Style cleanup when (unpacking, tuples); remove unneeded parens
* Remove redundant non-equivalence tests that are already tested
  due to non-ambiguity of LALR tables
* Add tests for power VS multiplicative operator precedence
Parser test: Add type parsing tests
Parser test: Rename state argument to start
Parse test: Add docstrings for assert methods
Parse test: Add tests for -> precedence & associativity
Parse test: Add regression test for int -> int ref
Parse test: Constructor VS not/delete precedence
Enable unittest after #41 is fixed
Type: Refactor imports.