All of the fixes discussed in the email

Hi,

Attached in this pull request are the improvements in separate commits:
* Bugfix:  Inject correct css file names into the two "all.css" files.
* Updated to the latest paymill gem (0.5.0)
* Updated the javascript a bit so that it uses the same method of initing as spree does. (this ensures that you can include jquery at the bottom of your HTML, in your  current source, the inlined javascript fails when jquery is included at the bottom)
* Added a guard around payment creation (in create_profile) to ensure the payment is not created twice. This happened to me since I have a separate "confirm this order" after the payment details.

In addition I relaxed the gemspec dependencies in my last commit to >= 2.2.0 which I hope would ensure that you can use it also on the 2-2-branch.  

I'm not that used to creating pull requests, so please let me know if I can improve anything.