Add error notification when ava is not found (#17)

Author: relekang

lib/terminal-command-executor.js

@@ -39,6 +39,12 @@ class TerminalCommandExecutor extends EventEmitter {
 }
 
 _streamClosed(code) {
+if (code === 127) {
+atom.notifications.addError('[AVA] Command not found', {
+detail: 'AVA was not found. Make sure it\'s installed.',
+dismissable: true
+});
+}
 this.emit(this.dataFinishedEventName, code);
 }
 }