loosen jquery version dependency

The previous jQuery version dependency tied the plugin to version 1.7,
not 1.7.1 or higher. I'm assuming this is compatible with 2.X too, so
loosened it to >=1.7. If it's not 2.X compatible, you could tighten it
to ~1.7 for all 1.X releases after 1.7
Merge pull request #204 from fidothe/fix-jquery-bower-dep

loosen jquery version dependency