Tidy up some deprecated code

[codecov[bot]]

Codecov Report

Merging #78 into master will increase coverage by 3.70%. The diff coverage is 85.88%.

@@            Coverage Diff             @@
##           master      #78      +/-   ##
==========================================
+ Coverage   78.72%   82.42%   +3.70%     
==========================================
  Files           1        1              
  Lines         517      495      -22     
==========================================
+ Hits          407      408       +1     
+ Misses        110       87      -23     

Impacted Files	Coverage Δ
tvdb_api.py	82.42% <85.88%> (+3.70%)	:arrow_up:

[dbr]

This is mostly good, just need to fix the stub-cache format under Python 2 (pickle format is incompatible between the two, even with older pickle format some of the methods are different)

May just bypass the stubs on Python 2 as they will be released in the next major version