[feature] Better loading indicator

- Use react-topbar-progress-indicator as a global loading indicator.
- Added a global reducer that only holds `isFetching` for now.
- Display loading indicator on any `*_REQUEST` actions.
- Closes #103

src/reducers/global.js

@@ -0,0 +1,17 @@
+/* Reducer for some global UI state that we want to share between components
+* Now being used for isFetching state to display global loading indicator
+* */
+
+const globalReducer = (state = { isFetching: false }, action) => {
+  if ((action.type.indexOf('REQUEST') > -1)) {
+    return { isFetching: true };
+  } else if (
+    (action.type.indexOf('SUCCESS') > -1) ||
+    (action.type.indexOf('FAILURE') > -1)
+  ) {
+    return { isFetching: false };
+  }
+  return state;
+};
+
+export default globalReducer;

src/reducers/index.js

@@ -7,6 +7,7 @@ import editorialWorkflow, * as fromEditorialWorkflow from './editorialWorkflow';
 import entryDraft from './entryDraft';
 import collections from './collections';
 import medias, * as fromMedias from './medias';
+import global from './global';
 
 const reducers = {
   auth,
@@ -18,6 +19,7 @@ const reducers = {
   editorialWorkflow,
   entryDraft,
   medias,
+  global,
 };
 
 export default reducers;