Add Django 1.10 support

[sergei-maertens]

☑ Add Django 1.10 to the build config ☑ Drop < 1.8 support ☑ Fix 1.10 issues ☑ Update docs/readme

Since Django 1.7 is not officially supported by Django core anymore, it makes sense to drop support. This also allows us to use the new TEMPLATES settings which makes testing a bit more enjoyable.

Currently the shipped widgets library is failing on 1.10, I'm not sure what changed, but it seems to be related to the {% for val, display in choices %} where the unpacking seems to be ... funky.

[coveralls]

Coverage remained the same at 72.196% when pulling 2c133ec400fac31fa81637a966421522beca5069 on sergei-maertens:feature/django-1.10 into 7ede278fc7f35470f2f241228d79d4cda6e20a84 on funkybob:master.

[codecov-io]

Current coverage is 70.30% (diff: 100%)

Merging #47 into master will increase coverage by 0.20%

@@             master        #47   diff @@
==========================================
  Files             2          2          
  Lines           428        431     +3   
  Methods           0          0          
  Messages          0          0          
  Branches         37         37          
==========================================
+ Hits            300        303     +3   
  Misses          119        119          
  Partials          9          9          

Powered by Codecov. Last update 7ede278...3bc72ab

[coveralls]

Coverage increased (+0.2%) to 72.39% when pulling 317a36e612e2f425db1634894bbd0754992d5aa6 on sergei-maertens:feature/django-1.10 into 7ede278fc7f35470f2f241228d79d4cda6e20a84 on funkybob:master.

[coveralls]

Coverage increased (+0.2%) to 72.39% when pulling 1d933f86eb34828ef23b699a8db790798f8a3270 on sergei-maertens:feature/django-1.10 into 7ede278fc7f35470f2f241228d79d4cda6e20a84 on funkybob:master.

[coveralls]

Coverage increased (+0.2%) to 72.39% when pulling 3bc72abaec33abfddafe01c5a4f48352a096ff40 on sergei-maertens:feature/django-1.10 into 7ede278fc7f35470f2f241228d79d4cda6e20a84 on funkybob:master.