Support other extensions than ".md"

Close #13.

lib/notational-velocity-view.coffee

@@ -17,7 +17,7 @@ class NotationalVelocityView extends SelectListView
     @skipPopulateList = false
     @prevCursorPosition = 0
     @documentsLoaded = false
-    @docQuery = new DocQuery(@rootDirectory, {recursive: true})
+    @docQuery = new DocQuery(@rootDirectory, {recursive: true, extensions: atom.config.get('nvatom.extensions')})
     @docQuery.on "ready", () =>
       @documentsLoaded = true
       @setLoading()
@@ -92,7 +92,8 @@ class NotationalVelocityView extends SelectListView
     item = @getSelectedItem()
     filePath = null
     sanitizedQuery = @getFilterQuery().replace(/\s+$/, '')
-    calculatedPath = path.join(@rootDirectory, sanitizedQuery + '.md')
+    extension = if atom.config.get('nvatom.extensions').length then atom.config.get('nvatom.extensions')[0] else '.md'
+    calculatedPath = path.join(@rootDirectory, sanitizedQuery + extension)
     if item?
       filePath = item.filePath
     else if fs.existsSync(calculatedPath)

lib/notational-velocity.coffee

@@ -9,6 +9,13 @@ module.exports =
       description: 'The directory to archive notes'
       type: 'string'
       default: path.join(process.env.ATOM_HOME, 'nvatom-notes')
+    extensions:
+      title: 'Extensions'
+      description: 'The first extension will be used for newly created notes.'
+      type: 'array'
+      default: ['.md', '.txt']
+      items:
+        type: 'string'
     enableLunrPipeline:
       title: 'Enable Lunr Pipeline'
       description: 'Lunr pipeline preprocesses query to make search faster. However, it will skip searching some of stop words such as "an" or "be".'