Add apmchi module to support github.com/go-chi/chi

[rliebz]

Create an apmchi module in modules/, which allows users to create middleware to log to Elastic APM. Does the standard apmhttp stuff, but also handles parametrized paths.

It can be used as follows:

r := chi.NewRouter()
r.Use(apmchi.Middleware())

Resolves #494

[axw]

Thank you @rliebz, this is looking great!

[axw]

jenkins run the tests please

[codecov-io]

Codecov Report

Merging #495 into master will increase coverage by 0.17%.
The diff coverage is 94.11%.

@@            Coverage Diff             @@
##           master     #495      +/-   ##
==========================================
+ Coverage   83.64%   83.81%   +0.17%     
==========================================
  Files         113      113              
  Lines        6566     6550      -16     
==========================================
- Hits         5492     5490       -2     
+ Misses        772      760      -12     
+ Partials      302      300       -2

Impacted Files	Coverage Δ
module/apmchi/middleware.go	94.11% <94.11%> (+20.11%)	⬆️
module/apmhttp/ignorer.go	50% <0%> (+16.66%)	⬆️

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[rliebz]

Not sure what makes Jenkins fail whenever I push, but otherwise I think it's good to go.

[axw]

Thank you for the top quality PR!
LGTM, will merge after Jenkins is happy.

[axw]

Not sure what makes Jenkins fail whenever I push, but otherwise I think it's good to go.

Our Jenkins CI only runs when instructed to by @elastic folks, preventing damage by malicious PRs. I'll get it going.

[axw]

jenkins run the tests please