Don't alter an existing control digit, even if its wrong
Merge pull request #3 from popgiro/master

Don't alter an existing control digit, even if its wrong
Updated the list of dependencies
Bumped the version number to 0.0.7
Updated the spec to verify that the control digit isn’t altered, even if it is invalid.
Object#blank? is not in the Ruby standard library.

Corrected an indentation error and renamed an overshadowed variable.
Updated the Changelog with the 0.0.7 release information.