[#35,all][m]: crude error catching for backends based on timeouts (best we can do with JSONP) - fixes #35.

* Show errors in UI
* required some extensive refactoring to use done/fail on promise rather than then

src/view.js

@@ -142,10 +142,14 @@ my.DataExplorer = Backbone.View.extend({
 
     // retrieve basic data like headers etc
     // note this.model and dataset returned are the same
-    this.model.fetch().then(function(dataset) {
-      self.el.find('.doc-count').text(self.model.docCount || 'Unknown');
-      self.query();
-    });
+    this.model.fetch()
+      .done(function(dataset) {
+        self.el.find('.doc-count').text(self.model.docCount || 'Unknown');
+        self.query();
+      })
+      .fail(function(error) {
+        my.notify(error.message, {category: 'error', persist: true});
+      });
   },
 
   query: function() {
@@ -158,6 +162,10 @@ my.DataExplorer = Backbone.View.extend({
       .done(function() {
         my.clearNotifications();
         my.notify('Data loaded', {category: 'success'});
+      })
+      .fail(function(error) {
+        my.clearNotifications();
+        my.notify(error.message, {category: 'error', persist: true});
       });
   },