Allow passing of options to the underlying request library.

A new optional argument to the class constructor is passed into all
calls to the request library. Use cases:
- The json endpoint you're talking to demands some custom header on all
  requests
- You need to turn off ssl cert validation
- You need to change the timeout
- Any of the other options provided by the request lib
Remove json from delete method (#copypastefail)
add Stephen to contributors
0.4.5