Improve Sinatra and Padrino Tracing

We only offer basic/manual Sinatra and Padrino tracing.  This can be expanded to report on Sinatra specific components and internals.

'How to instrument' documentation is [here](https://github.com/appneta/oboe-ruby#sinatrapadrino).

Sample traces from a Sinatra app that uses the supported mongo library:
https://dumana.tv.appneta.com/traces/view/621A4657ED6BE53E0D2E554B55DB319E841B43D7#
https://dumana.tv.appneta.com/traces/view/579CC075CE2EFE617C4224540687387D4D67BF59#

Support should be added to hook into some of the internals of the Sinatra framework and to report controller/action type KVs.

#### Tasks

- [x] Auto insert `Oboe::Rack` middleware
- [ ] Instrument template rendering
- [ ] Report Controller/Action KVs as best fit
- [ ] Auto configure Oboe.logger into Sinatra logger
- [ ] Test against Modular vs. Classic Style Sinatra Apps
- [ ] Instrument and report on Streaming Responses?
- [ ] Identify Padrino superset items to instrument