Lex test: Rewrite commented-out test as skipped test.
Lex test: Expand testing of #8.
Lex test: Make assertions more sure-y (and less verbose, where possible).
Lex test: Fix some pylint warnings.
Parse test: Make assertions less verbose.

* Use `equal` when __eq__ invocation is implied.
* Use `be` to test against None.
Parse test: Fix some pylint warnings.
Parse test: Use skip decorator instead of SkipTest Exception.
Parse test: Fortify tests to check that order is preserved.
Parse test: Make assertions more sure-y.
Parse test: Beautify code.
Parse test: Fix bad prerequisite.
Parse test: Replace reference to class with self.
Parse test: Fortify tests.

* Differentiate expressions used as AST nodes to avoid undetected
  errors in argument order of AST constructors.
* Make tests more readable, by using semantically correct code.
AST test: Use skip decorator instead of SkipTest Exception.
AST test: Make assertion more sure-y.
AST test: Beutify and fix some pylint warnings.
Tests: Import sure at package level, as is recommended.
Type test: Make testing less verbose.
Type test: Fix some pylint warnings.
Makefile: Create separate unittest script. Rename functionaltest script.