Updated classes to the new HasError interface (with helper texts).

Author: Gilberto Torrezan Filho

src/main/java/gwt/material/design/addins/client/autocomplete/MaterialAutoComplete.java

@@ -541,6 +541,11 @@ public void setError(String error) {
     public void setSuccess(String success) {
         errorMixin.setSuccess(success);
     }
+    
+    @Override
+    public void setHelperText(String helperText) {
+        errorMixin.setHelperText(helperText);
+    }
 
     @Override
     public void clearErrorOrSuccess() {

src/main/java/gwt/material/design/addins/client/stepper/MaterialStep.java

@@ -173,6 +173,11 @@ public void setSuccess(String success) {
         addStyleName("success");
         applyIconStatus(iconSuccess, "blue", success);
     }
+    
+    @Override
+    public void setHelperText(String helperText) {
+        setDescription(helperText);
+    }
 
     @Override
     public void clearErrorOrSuccess() {

src/main/java/gwt/material/design/addins/client/stepper/MaterialStepper.java

@@ -293,6 +293,11 @@ public void setError(String error) {
     public void setSuccess(String success) {
         getCurrentStep().setSuccess(success);
     }
+    
+    @Override
+    public void setHelperText(String helperText) {
+        getCurrentStep().setDescription(helperText);
+    }
 
     @Override
     public void clearErrorOrSuccess() {

src/main/java/gwt/material/design/addins/client/timepicker/MaterialTimePicker.java

@@ -203,6 +203,11 @@ public void setError(String error) {
     public void setSuccess(String success) {
         this.errorMixin.setSuccess(success);
     }
+    
+    @Override
+    public void setHelperText(String helperText) {
+        this.errorMixin.setHelperText(helperText);
+    }
 
     @Override
     public void clearErrorOrSuccess() {