Merge pull request #4 from sba/master

Option to disable mousewheel
Merge pull request #5 from sba/master

handling of inputs with empty value
Fixes #2
Updated demo page with the mousewheel setting.
Fixes #6
Fixes #7
Now can add extra class(es) for prefix and postfix.
Added postfix_extraclass demo.
Fixes #8
Fixes #9 - The plugin now can be initialized on an input-group.
Fixes #10
Always adding form-control class to input