fix(select): make aria compliant, read value in screen readers

closes #3891, closes #4914, closes #4977, closes #6000, closes #3859

Author: rschmukler

docs/app/js/preload.js

@@ -98,7 +98,7 @@ function labelDirective() {
     restrict: 'E',
     require: '^?mdInputContainer',
     link: function(scope, element, attr, containerCtrl) {
-      if (!containerCtrl || attr.mdNoFloat) return;
+      if (!containerCtrl || attr.mdNoFloat || element.hasClass('md-container-ignore')) return;
 
       containerCtrl.label = element;
       scope.$on('$destroy', function() {

src/components/input/input.js

@@ -87,14 +87,14 @@ md-input-container {
     -ms-flex-preferred-size: auto; //IE fix
   }
 
-  label {
+  label:not(.md-container-ignore) {
     position: absolute;
     bottom: 100%;
     left: 0;
   }
 
 
-  label:not(.md-no-float),
+  label:not(.md-no-float):not(.md-container-ignore),
   .md-placeholder {
     order: 1;
     pointer-events: none;