Add linting and docs builds to CI

[rpkilby]

No description provided.

[codecov-io]

Codecov Report

Merging #850 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #850      +/-   ##
==========================================
+ Coverage   97.95%   97.95%   +<.01%     
==========================================
  Files          15       15              
  Lines        1122     1124       +2     
==========================================
+ Hits         1099     1101       +2     
  Misses         23       23

Impacted Files	Coverage Δ
django_filters/filterset.py	100% <ø> (ø)	⬆️
django_filters/rest_framework/filters.py	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a88c2bc...4beb61d. Read the comment docs.