Add some Sphinx Directives that need to be ignored.

According to [issus#1](https://github.com/myint/rstcheck/issues/1), we need to ignore some Sphinx Directives because docutils doesn't support all the newest Sphinx tags. Thus, I add some other Sphinx Directives in addition to `toctree`. **More details please see rstcheck.py line 175**.

However, I think we need to fix module `docutils.parsers.rst.languages.en` if we want to fix this bug completely