chore(requirements): update Django and supporting libraries

[mboersma]

See https://docs.djangoproject.com/en/1.11/releases/1.11.2/ and https://github.com/jmespath/jmespath.py/blob/develop/CHANGELOG.rst#093 and https://github.com/litl/backoff/blob/master/CHANGELOG.md#v143---2017-05-22 and https://github.com/pyldap/pyldap/blob/master/CHANGES

[codecov-io]

Codecov Report

Merging #1303 into master will decrease coverage by 0.07%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1303      +/-   ##
==========================================
- Coverage   87.07%   86.99%   -0.08%     
==========================================
  Files          45       45              
  Lines        3929     3929              
  Branches      681      681              
==========================================
- Hits         3421     3418       -3     
- Misses        337      339       +2     
- Partials      171      172       +1