add !important to enable placeholder styling in IE

src/definitions/collections/form.less

@@ -344,7 +344,7 @@
   color: @inputErrorPlaceholderColor;
 }
 .ui.form .error :-ms-input-placeholder {
-  color: @inputErrorPlaceholderColor;
+  color: @inputErrorPlaceholderColor !important;
 }
 .ui.form .error ::-moz-placeholder {
   color: @inputErrorPlaceholderColor;
@@ -354,7 +354,7 @@
   color: @inputErrorPlaceholderFocusColor;
 }
 .ui.form .error :focus:-ms-input-placeholder {
-  color: @inputErrorPlaceholderFocusColor;
+  color: @inputErrorPlaceholderFocusColor !important;
 }
 .ui.form .error :focus::-moz-placeholder {
   color: @inputErrorPlaceholderFocusColor;

src/definitions/elements/input.less

@@ -188,7 +188,7 @@
   color: @placeholderErrorColor;
 }
 .ui.input.error input:-ms-input-placeholder {
-  color: @placeholderErrorColor;
+  color: @placeholderErrorColor !important;
 }
 
 /* Focused Error Placeholder */
@@ -199,7 +199,7 @@
   color: @placeholderErrorFocusColor;
 }
 .ui.input.error input:focus:-ms-input-placeholder {
-  color: @placeholderErrorFocusColor;
+  color: @placeholderErrorFocusColor !important;
 }
 
 /*******************************