LPC-132 standardizing logging
As cute as The Foo's homepage is, lets not use it in examples
Merge pull request #13 from laterpay/feature/LPC-132-standardizing-logging

LPC-132 standardizing logging
Merge pull request #17 from laterpay/feature/use-invalid-urls

As cute as The Foo's homepage is, lets not use it in examples
There is no need to define `__init__` nor `__repr__` for a simple exception class like InvalidItemException.
Merge pull request #18 from laterpay/feature/strip-invaliditemexception-init

No need to define `__init__` nor `__repr__` for InvalidItemDefinition
Added a regression test for expiry param equal to 'None'.

For a not expiring item.
Discard `None` params in `LaterPayClient._get_web_url()`

We don't want to create urls containing "param=None" bits
if a param is optional.
Don't use `django.shortcuts.redirect` if not necessary.

A simple HttpResponseRedirect is enough here.
Merge pull request #20 from laterpay/feature/no-need-to-use-redirect-over-httpresponseredirect

Don't use `django.shortcuts.redirect` if not necessary.
Added `LPTokenMiddleware.exempt_paths()`.
Added django to test requirements.
Merge pull request #21 from laterpay/feature/add-exempt-paths-to-lptoken-middleware

Added `LPTokenMiddleware.exempt_paths()`.
Merge pull request #19 from laterpay/feature/fix-expiry-param-as-None-in-url

Discard `None` params in `LaterPayClient._get_web_url()`
Merge branch 'develop' into feature/tox

Conflicts:
	.travis.yml