Fix memory leaks

[Leo1003]

Here are the two memory leaks I currently found in this repository:

• Unneeded strdup() in src/linux/InotifyEventLoop.cpp
  • This is easy to fix. Just to remove strdup function call and just pass a C-string; C++ string will make a copy by itself.
• Not every call to uv_async_send() will yield an execution of the callback (Document).
  • mEventCallbackAsync may not be called. As a result, EventBaton and its events won't be freed by cleanupEventCallback()
  • Also cause event missing.
  • This bug is not easy to fix, since it may need to change the method to pass events in order to fix it.

This pull request currently fixed the first leaks.
Related to #72

[implausible]

Excellent find on both issues. Thanks for fixing the first issue. As to the second issue, perhaps we need to use a mutex and a long living event queue that we can queue / dequeue from on all threads involved.