Added call to init method of custom provider so it would work as described at README.
Add tests for custom providers load&usage
Add Rutube provider
Remove Justin.TV because it is no longer in service
Add Promise support
Add .idea folder to .gitignore
Make passing to a callback more concise
Merge branch 'custom-provider-fix'
Merge branch 'remove-justine-tv'
Merged with add-rutube-provider branch.
Merge branch 'add-promise-support'
Add custom errors for two cases:
- Url that was passed in embed.get method is malformed or invalid.
- There is no registered provider for this url.
Switched from native Promises to the Bluebird  because of it's awesome .spread, .nodeify and .promisifyAll methods.
Add Embed.ly fallback for urls without providers.
Increased minor version for non-breaking API change, updated README.