Add noop implementation of newrelic.Application and newrelic.Transaction

[v-yarotsky]

Useful for tests and in cases where it's impossible to initialize the
actual newrelic.Application instance, but the app needs to run
regardless.

I can add it to our wrapper library, but I thought it might be useful to others as well.

[jairodasilva]

I don't think this is necessary. You can use counterfeiter to generate your fakes. I use this tool in my project to fake/mock the Application and Transaction interfaces.

[willnewrelic]

Hi v-yarotsky

Thanks for the PR. We appreciate your desire to contribute.

For legal purposes, we have just updated the LICENSE.txt with additional information about contributions. Please take a look. As a result, I'm going to have to close this PR and ask you to resubmit it. I'm sorry for the inconvenience.

[purple4reina]

Hello @v-yarotsky!

We've recently published some proposed changes to the agent for a 3.0 major version release #106. We're wondering what you think of these changes and if they will fit your needs.

Particularly, we're proposing changing newrelic.Application and newrelic.Transaction from interfaces to structs. This would remove the requirement for nil checks throughout your code and/or a noop Application and Transaction. Please take a look at it and let us know what you think!