Drop support for Python 3.3.
Install coverage package.

* Ignore coverage byproduct.
Drop utest script. Report test coverage.
Enable coveralls support.

* Install a coverage badge.
* Invoke coveralls.io after a successful build.
Mention flake8 instead of pep8.
Merge pull request #72 from Renelvon/coveralls

[WIP] Install coveralls and cleanup build.
Type, Type test: Unify error hierarchy.
Type test: Static methods are no more.
Type test: Move is_array tests in separate class.
Type test: [TDD] Move validation inside Table.
Type: Move validation inside Table.
Type test: Simplify code.
Type: Move is_array.
Type test: [TDD] Signal undefined type when validating.
Type: Signal undefined type when validating.
Type test: [TDD] Validate arguments of constructors.
Type: Validate arguments of constructors.
Errata: Sort entries.
Errata: Constructor arguments should be valid types.
Type test: Verify API of Table.