Added convenient methods for uploading files.

[adelowo]

Implements go-aah/aah#82

[codecov]

Codecov Report

Merging #15 into v0-unstable will decrease coverage by 0.35%.
The diff coverage is 90.32%.

@@               Coverage Diff               @@
##           v0-unstable      #15      +/-   ##
===============================================
- Coverage        98.45%   98.09%   -0.36%     
===============================================
  Files                6        6              
  Lines              389      421      +32     
===============================================
+ Hits               383      413      +30     
- Misses               5        6       +1     
- Partials             1        2       +1

Impacted Files	Coverage Δ
request.go	98.02% <90.32%> (-1.15%)	⬇️

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[jeevatkm]

@adelowo You have nicely written test case. Very important one. Thank you for the PR.

I'm merging it.