Remove restriction for jQuery version in bower.json

This was needed since Ember v1.3.1 only works with jQuery <2.1, but the
bower config for this version didn't specify this restriction. Since
this has been fixed by Señor @rjackson (http://git.io/B2xRbQ) the
specific jQuery version is removed again from `bower.json`.
Merge pull request #1710 from pangratz/remove_jquery_dependency_in_bower

Remove restriction for jQuery version in bower.json