I get "Could not parse version constraint <=2.1.x: Invalid version string "2.1.x"" when attempting to install jquery-modal. I am requiring "bower-asset/jquery-modal": "~0.5.2". This seems similar to #55.

The library's bower.json file specifies a version like this:

"jquery": "1.8.0 - 2.1.x"

https://github.com/kylefox/jquery-modal/blob/master/bower.json