fix to center icon inside md-button ...
fix to center icon inside md-button ...

same like md-icon
sscovil/angular-material-icons,adrianha/angular-material-icons,archfirst/angular-material-icons,klarsys/angular-material-icons,JSMike/angular-material-icons,2947721120/angular-material-icons,waysay/angular-material-icons,archfirst/angular-material-icons,mennya/ny-angular-material-icons,JSMike/angular-material-icons,Aalisha/angular-material-icons,apadol/angular-material-icons,klarsys/angular-material-icons,Aalisha/angular-material-icons,2947721120/angular-material-icons,adrianha/angular-material-icons,waysay/angular-material-icons,apadol/angular-material-icons,mennya/ny-angular-material-icons,sscovil/angular-material-icons