Added osx stuff
Added webmock
Stubbed two examples with webmock and fixed a bug where instruments where submitted wrongly to the API
More flexibility in instruments test
Updated fields filtering example for webmock
Removed unnecessary call
Updated example for authorization to webmock and added a second example to see if Instrument requests Authorization details
Resolved issue #25
Merge branch 'develop' of https://github.com/phikes/oanda into develop