Added Docker::Image#create_from_file.

This method allows the creation of an Image from a Container's
export.
Updated the README to include Docker::Image#create_from_file
Now setting the proper headers.

If Docker decides to reject more requests based on the incorrect headers
in the future, this gem will be covered.
Version bump 0.0.5
Added a travis configuration file.

Right now, I'm specifying every Ruby version. We'll see how this build
goes and that will determine which we keep.
Updated the travis configuration file.

Appearently, only Ruby 1.9.2+ will build.
Now mocking the File.open operation in the Image#create_from_file spec.
Merge pull request #7 from swipely/improve-image-create

Improve image create