[MRG+1] fix headers_raw_to_dict multiple headers with one name issue

[dmippolitov]

#84

[codecov-io]

Codecov Report

Merging #85 into master will increase coverage by 0.12%.

@@            Coverage Diff             @@
##           master      #85      +/-   ##
==========================================
+ Coverage   94.13%   94.25%   +0.12%     
==========================================
  Files           7        7              
  Lines         409      418       +9     
  Branches       85       87       +2     
==========================================
+ Hits          385      394       +9     
  Misses         16       16              
  Partials        8        8

Impacted Files	Coverage Δ
w3lib/http.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 a997816...c3e61bc. Read the comment docs.

[kmike]

Looks good, thanks @dmippolitov!