Added Content-Type support for SetFileReader

[gh0st42]

Simple solution to set content type for multipart filereader parts. Default resty behaviour of "application/octet-stream" still present if no content-type is given.

[codecov]

Codecov Report

Merging #111 into master will decrease coverage by 0.83%.
The diff coverage is 62.5%.

@@            Coverage Diff             @@
##           master     #111      +/-   ##
==========================================
- Coverage   96.96%   96.12%   -0.84%     
==========================================
  Files          10       10              
  Lines         987     1006      +19     
==========================================
+ Hits          957      967      +10     
- Misses         16       25       +9     
  Partials       14       14

Impacted Files	Coverage Δ
client.go	97.62% <100%> (ø)	⬆️
util.go	93.81% <100%> (+0.63%)	⬆️
request.go	94.76% <30.76%> (-5.24%)	⬇️

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[jeevatkm]

@gh0st42 Thanks for the PR. While looking at your PR, I think we can do better for SetFileReader and SetFile together with backward compatibility.

Let me create a PR, then you can have a look and we can improve it.

[gh0st42]

Sounds good, if you have a special testing branch this would also be fine and I'd be happy to test it. I guess for a general solution that can be applied to SetFileReader as well as SetFile a bit more work has to be done since currently they are implemented both a bit different in resty.

[jeevatkm]

Closing this PR infavour of generic implementation 513d3b0