add headers argument to upload_file and store_object

[joeshaw]

Added to both the client and container versions of these functions. This is
primarily to add support for setting Content-Encoding: gzip to uploaded files.

See
http://docs.rackspace.com/files/api/v1/cf-devguide/content/Enabling_File_Compression_with_the_Content-Encoding_Header-d1e2198.html

[EdLeafe]

This is a good addition, but I'd like to see it consistent with the rest of the parameters. 'Content-type' is passed as the named parameter content_type; it would be better to add a content_encoding parameter as well to the method signatures, and then convert to the headers argument when calling swiftclient.

The goal of an SDK is to smooth out the warts of the underlying APIs, making development more consistent. The fact that swiftclient accepts named params for some things and not others is a wart IMO.

[joeshaw]

Force pushed an updated commit to my branch (d2d812b).

[joeshaw]

Opened #67 with an updated patch, since this one was closed.