move Dialog analytics to Modal controller

mark title as required, it sorta is, why isn't this based on BaseDialog?

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/Modal.js

@@ -19,6 +19,7 @@ limitations under the License.
 
 var React = require('react');
 var ReactDOM = require('react-dom');
+import Analytics from './Analytics';
 import sdk from './index';
 
 const DIALOG_CONTAINER_ID = "mx_Dialog_Container";
@@ -104,6 +105,7 @@ class ModalManager {
     }
 
     createDialog(Element, props, className) {
+        Analytics.trackEvent('Modal', props.title, 'createDialog');
         return this.createDialogAsync((cb) => {cb(Element);}, props, className);
     }