Extract GCP Monitoring

[marwan-at-work]

• Created a new gcputil package (following ioutil/serverutil pattern)
• Moved helpful initialization functions out of server/kit into the new package so that SimpleServer or really any Go program can initialize metrics/tracing.
• Added a new function RegisterOpenCensus which makes it easier for the user to just call this function, without having to manually get the metadata, insert them into the opts, get the opts, insert the opts into the Exporter.
• I bet server/kit can probably use RegisterOpenCensus with some refactoring in the future

fixes #185

[coveralls]

Coverage increased (+0.6%) to 46.98% when pulling ba9794e on marwan-at-work:gcp into 9eaa369 on NYTimes:master.

[jprobinson]

Made some comments regarding the package name and how things get registered. Lemme know what you think.

[marwan-at-work]

@jprobinson all comments should be addressed, happy to revise more

[jprobinson]

I've made a few notes but this is a great start!

[marwan-at-work]

@jprobinson all comments addressed

[jprobinson]

Mind also adding a mention of this new package in the repo README?

[marwan-at-work]

@jprobinson i fixed the Go doc, there was already a mention of those variables in the main README, but i also added them to the server/kit README

[marwan-at-work]

@jprobinson fixed the onErr message, let me know if there's anything else that needs updating. Thanks!

[jprobinson]

Ah shoot, sorry. I just noticed we're referencing the mention in the root README.md of the project. The blurb used for the project level doc should be fine.

[jprobinson]

📈 ! 🌯 ! Thanks for your patience, @marwan-at-work!