Add config to requests for $http

This should allow users to add all $http config options to requests:

- [x] Allow passing config on individual instance calls
- [x] Allow passing config when request is configured
- [x] Allow passing config for an entire Constructor

Need to ensure that the proper order is followed

1. Instance calls with their config should overwrite all others
2. Any config passed to a request config should override defaults for the class
3. Any config passed to class is the default for all class calls

Fixes #1