Update _input-forms.scss to work on FireFox
Update _input-forms.scss to work on FireFox

On FireFox v49.0.1, the `label` gets fixed incorrectly to the right of the input field, instead of flushed with the input field at the left margin. 
Adding `left: 0` fixes this immediately, with no foreseeable consequences.
josecarlosweb/materialize,digitalkaoz/materialize,ccloli/materialize,ZiperRom1/materialize,INGCRENGIFO/materialize,tomscholz/materialize,Dogfalo/materialize,Dogfalo/materialize,ManuZiD/materialize,INGCRENGIFO/materialize,digitalkaoz/materialize,josecarlosweb/materialize,tomscholz/materialize,ZiperRom1/materialize,ccloli/materialize,ManuZiD/materialize