Install Django version first, then requirements in Travis

[michael-k]

This PR installs the specific Django version first, before installing requirements.txt. This means Travis will no longer install whatever Django version first, and instead will look something like:

$ pip install Django==$DJANGO_VERSION
Collecting Django==1.8.18
  Downloading Django-1.8.18-py2.py3-none-any.whl (6.2MB)
    100% |████████████████████████████████| 6.2MB 262kB/s 
Installing collected packages: Django
Successfully installed Django-1.8.18

$ pip install -r requirements.txt
Requirement already satisfied: Django in /home/travis/virtualenv/python3.6.3/lib/python3.6/site-packages (from -r requirements.txt (line 3))

[codecov]

Codecov Report

Merging #54 into develop will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           develop    #54   +/-   ##
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  Coverage      100%   100%           
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  Files            3      3           
  Lines           23     23           
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  Hits            23     23

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[urda]

Hey!

I wanted to drop in and say THANKS for the contribution.

I’m on the road for now, but this week I’ll try to get a review in for this later this week. I also have a local branch with similar changes to compare with first so I’m not sure if this is already covered already.

Thanks again, and I’ll get back to this shortly.

[urda]

Hi @michael-k , I'm going to hold off on the Django version bump as I already have a local branch I'm working on to support it. It was also dropping support for another version, and I normally do not like doing two different tasks like that in a single PR.

HOWEVER I do love you fixed up travis to install the Django version first. I'm signing that commit, and preparing this for a merge.

[urda]

Restored old commits to this PR, closing in favor of #55