Type convert boolean variables correctly (closes #149)

[tommilligan]

See #149 for issue details.

This PR:

• adds failing tests that show !bool type conversion is incorrect
• implements a fix for !bool using a custom bool constructor class

The custom bool constructor is similar to the builtin bool constructor as per PEP 285, and as discussed here

[michaelboulton]

Rather than using a custom constructor it is probably better to use strtobool from the standard library, which can handle a lot more than just True and False (including all the weird yaml ones like on and y)

Other than that, this all looks good!

[tommilligan]

Happy to use strtobool instead, if it's okay to allow a wider range of values. Agree it's better than a custom implementation.

See the new commit for changes:

• it still has to be wrapped in a constructor __new__ method to match other constructors
• strtobool actually returns 0|1, so it's wrapped in bool

[tommilligan]

There is a long running known issue with combining distutils, pylint and virtualenv (which tox uses internally). pylint reports a false positive that distutils cannot be found.

I have added distutils as an ignored module in .pylintrc.

[michaelboulton]

Thanks for that, it should be deployed in version 0.15.1.

[tommilligan]

@michaelboulton PyPI latest version appears to be 0.14.4 - have had a quick look at the Travis logs and can't see any obvious errors

[michaelboulton]

It seems like the deplyment via travis isn't actually deploying - I don't have time to look at this until monday though unfortunately,

I might just change it so it's using gitlab CI to do the deployment