Django-laterpay

* Added full support for Django 1.8, 1.9 and 1.10
* Requires Python 2.7 or Python 3.4+
* Removed official support for Django before 1.8
* Removed official support for Python 3.3
* Removed official support for laterpay-client before 4.1
* Removed deprecated template tags `render_laterpay_header`, `render_laterpay_footer`, `laterpay_subscribe`, and `laterpay_buy` from `djlaterpay`
* Removed now unused template tags template files `laterpay/inclusion/render_footer.html` and `laterpay/inclusion/render_header.html`

* Loosened version requirement for `laterpay-client` (so it could use v4.0.0 and higher).

* Support and testing for all supported Django versions (1.6 as originally, plus 1.4 and 1.7 and 1.8)
* Added [logging to LPTokenMiddleware](https://github.com/laterpay/django-laterpay/pull/12)
* Bumped [laterpay-client](https://github.com/laterpay/laterpay-client-python) dependency to 3.2.1

* Bumped [laterpay-client](https://github.com/laterpay/laterpay-client-python) dependency to 3.1.0
* Deprecated `djlaterpay.templatetags.laterpay` module
* Added verification for lptokens [received in middleware](https://github.com/laterpay/django-laterpay/pull/5)
* MANIFEST.in fixes
* pep8 fixes

Existence