Autoclass

* improved validators list documentation
* added new validator: `and_`
* fixed bugs in `or_`, `not_`, and `xor_` : since custom validators may now throw exceptions other than `ValidationError` and may return `None`, there was a need to update them to take these cases into account
* `not_` may now be applied to a list of validators (implicit `and_`)
* more unit tests for boolean validators

* A validator function may now return `None`
* improved documentation on `validate` in particular for custom validators implementation

* New: `validate` annotation allowing to implement input validation. Comes with a bunch of built-in validators.

* Improved documentation
* Automatic test report generation in travis
* Automatic PyPI deployment on tags in travis

* `classtools-autocode` Project was renamed `autoclass` for clarity
* Travis configuration was updated accordingly

* improved examples in the documentation
* improved performance of var_checker (lessons learnt from parsyfiles)