Use existing file metadata for created and modified dates

NB: this definintely works on OSX. Other operating systems may have
slightly different interpretations of birthtime.

See: https://nodejs.org/api/fs.html#fs_class_fs_stats

browser/main/NoteList/index.js

@@ -584,12 +584,18 @@ class NoteList extends React.Component {
     filepaths.forEach((filepath) => {
       fs.readFile(filepath, (err, data) => {
         if (err) throw Error('File reading error: ', err)
+
+        fs.stat(filepath, (err, {mtime, birthtime}) => {
+          if (err) throw Error('File stat reading error: ', err);
+
           const content = data.toString()
           const newNote = {
             content: content,
             folder: folder.key,
             title: markdown.strip(findNoteTitle(content)),
-          type: 'MARKDOWN_NOTE'
+            type: 'MARKDOWN_NOTE',
+            createdAt: birthtime,
+            updatedAt: mtime
           }
           dataApi.createNote(storage.key, newNote)
           .then((note) => {
@@ -604,6 +610,7 @@ class NoteList extends React.Component {
           })
         })
       })
+    })
   }
 
   getTargetIndex () {

browser/main/lib/dataApi/createNote.js

@@ -66,12 +66,12 @@ function createNote (storageKey, input) {
           }
         }
       }
-      const noteData = Object.assign({}, input, {
+      const noteData = Object.assign({}, {
         key,
         createdAt: new Date(),
         updatedAt: new Date(),
         storage: storageKey
-      })
+      }, input)
 
       CSON.writeFileSync(path.join(storage.path, 'notes', key + '.cson'), _.omit(noteData, ['key', 'storage']))