Remove pubspec.lock from git (#58)

* Remove pubspec.lock from git

* Add new line at end of file

Author: nilsreichardt

.gitignore

@@ -9,4 +9,9 @@ build/
 
 .idea/
 *._*
-.flutter*
+.flutter*
+
+# Packages should not commit the "pubspec.lock" file. 
+#
+# See https://dart.dev/guides/libraries/private-files#pubspeclock
+/pubspec.lock