Allow for requests without headers to default to V1
Allows requests without headers to get the default version
Update Travis.

Test against 4.0.0, allow failures on 4-0-stable.
Ignore coveralls generated files.
Actually, don't allow failures on 4-0-stable.
Removes coverall coverage files and excludes the directory from git
Merge pull request #8 from CoryFoy:default_when_no_vendor_header

This closes #6. It changes the behavior to automaticallyinject the vendor
accept header if it is not provided.