added fetch snippet

refactored some code

fixed snippet content empty on changed from list

fixed snippet name not updating on list when changed

browser/main/lib/dataApi/index.js

@@ -16,6 +16,7 @@ const dataApi = {
   createSnippet: require('./createSnippet'),
   deleteSnippet: require('./deleteSnippet'),
   updateSnippet: require('./updateSnippet'),
+  fetchSnippet: require('./fetchSnippet'),
 
   _migrateFromV6Storage: require('./migrateFromV6Storage'),
   _resolveStorageData: require('./resolveStorageData'),