Beginning to add the ability to get other data formats.
- Modified Quandl.get() to accept 'csv', 'json', 'xml', or 'plain' as return format
- Added filename param to Quandl.get() for writing dataset to file
- Replaced Quandl._download() with Quandl._request()
- Rewrote error-handling for requests
- Added Quandl._write_to_file()
- Added Quandl._prepare_url() to handle adding dataset to QUANDL_API_URL
Forgot to return resp in Quandl.get()
Return response content
Fixed Quandl.get() when returns='url'
Fixed Quandl.get() when returns='url'
Fixed MissingSchema error for Quandl.get()
Added .travis.yml