Added docs for OkHttp integration (#144)
Added docs for OkHttp integration (#144)

Summary:
This PR includes documentation for using the `SonarOkhttpInterceptor` for applications using the `OkHttp` network stack. The docs were modelled on the [Stetho docs](http://facebook.github.io/stetho/#enable-network-inspection)

Fixes #22.
Pull Request resolved: https://github.com/facebook/Sonar/pull/144

Differential Revision: D8780506

Pulled By: danielbuechele

fbshipit-source-id: fb2ddd4356b421c3baf0a80a410dd579ebc1bd8d

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