Add Request.Send() method to execute Request as-is

[dan-rising]

Was working on a project recently that could have benefitted from something like this since the requests were constructed in a different place than they were actually sent.

You can already do this in Resty with something like this:

req := client.R()
req.URL = "http://httpbin.org/get"
req.Method = "GET"

resp, err := req.Execute(req.Method, req.URL)

It just feels a bit clunky to me.

[codecov]

Codecov Report

Merging #286 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #286      +/-   ##
==========================================
+ Coverage   95.48%   95.49%   +<.01%     
==========================================
  Files           9        9              
  Lines        1152     1154       +2     
==========================================
+ Hits         1100     1102       +2     
  Misses         29       29              
  Partials       23       23

Impacted Files	Coverage Δ
request.go	100% <100%> (ø)	⬆️

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[jeevatkm]

@dan-rising Thank you for the PR 👍