Move logout call away from the base class

[pipozzz]

Move logout call to separate api call + add test

Fix #50 #51 #54

[codecov]

Codecov Report

Merging #55 into master will increase coverage by 0.18%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #55      +/-   ##
==========================================
+ Coverage   86.71%   86.89%   +0.18%     
==========================================
  Files          24       25       +1     
  Lines         429      435       +6     
==========================================
+ Hits          372      378       +6     
  Misses         57       57              

Impacted Files	Coverage Δ
rocketchat/calls/base.py	79.62% <ø> (-1.41%)	⬇️
rocketchat/api.py	89.47% <100.00%> (+0.43%)	⬆️
rocketchat/calls/auth/logout.py	100.00% <100.00%> (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 54171ac...6c1c89e. Read the comment docs.