add codecov to the project

[malloxpb]

Hey @lopuhin , I added Codecov to this project. However, I am not sure if what I did was correct. Can you please check this when you have time? Thank you 😄

[codecov[bot]]

Codecov Report

Merging #19 into master will decrease coverage by 42.85%. The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #19       +/-   ##
========================================
- Coverage   42.85%    0%   -42.86%     
========================================
  Files           1     1               
  Lines           7     7               
  Branches        0     1        +1     
========================================
- Hits            3     0        -3     
- Misses          4     7        +3

Impacted Files	Coverage Δ
urlparse4/__init__.py	0% <0%> (-42.86%)	:arrow_down:

[lopuhin]

Would be also nice to have coverage of Cython source (see e.g. https://stackoverflow.com/a/48672858/217088), since almost all code is in Cython.

Also looking at the coverage report for this branch (https://codecov.io/gh/nctl144/urlparse4/branch/codecov) I see that "tests" folder is covered, which is normally not done - we want to track just the coverage of the project. Also for some reason urlparse4/__init__.py is shown as not covered... Btw, codecov also has an option to produce local reports as html, which can be useful for debugging such issues and checking coverage locally.

[malloxpb]

Hey @lopuhin , I tried to include Cython plugin in codecov but it does not seem to report the coverage of cython code. Do you know what I am missing?