Allow Sequential collections to be used in component/using

[mpenet]

Hi Stuart,

When building the list of dependencies for using dynamically we would often end up with a Sequential of some kind, right now there is a vector? check that will force the user to call vec/into [] prior to passing the dependencies to the function. I can't seem to find a reason not to allow other Sequentials.
You have a PR here with the necessary change to make it work: #27

[stuartsierra]

See #27