if isValidDate is passed we need to verify if the view date is valid … (arqex#296)

* if isValidDate is passed we need to verify if the view date is valid before trying to render the component.

Author: JesseChrestler

DateTime.js

@@ -192,7 +192,13 @@ var Datetime = createClass({
 				}
 			}
 		}
-
+		//we should only show a valid date if we are provided a isValidDate function.
+		if (this.props.isValidDate) {
+			updatedState.viewDate = updatedState.viewDate || this.state.viewDate;
+			while (!this.props.isValidDate(updatedState.viewDate)) {
+				updatedState.viewDate = updatedState.viewDate.add(1, 'day');
+			}
+		}
 		this.setState( updatedState );
 	},