removed canvas from devDependancies
removed canvas from devDependancies

Travis keeps failing because cairo isn't installed and our readme explains that it's needed anyway.
tj/nib,rstacruz/nib,JulianWielga/stylus-less,seleckis/nib-pushup,F4-Group/nib,ilovezy/nib,ilovezy/nib,seleckis/nib-pushup,tj/nib,F4-Group/nib,ecmartinez/nib,ecmartinez/nib