Eliminate Sphinx warning

    retools/queue.py:docstring of retools.queue:71: WARNING: Inline
    strong start-string without end-string

by escaping asterisks with backslashes.
conf.py: Comment out html_static_path

Gets rid of this Sphinx warning:

    copying static files... WARNING: html_static_path entry
    u'/Users/marca/dev/git-repos/retools/docs/_static' does not exist
api.rst: Add api/limiter to toctree

to prevent warning:

    /Users/marca/dev/git-repos/retools/docs/api/limiter.rst:: WARNING:
    document isn't included in any toctree
Change :app: role to :py:mod:

to prevent ":app:`retools`" from appearing in docs and to prevent
warning:

    /Users/marca/dev/git-repos/retools/docs/api.rst:4: ERROR: Unknown
    interpreted text role "app".
Correct label in limiter.rst

to prevent warning:

    /Users/marca/dev/git-repos/retools/docs/api/queue.rst:4: WARNING:
    duplicate label queue_module, other instance in
    /Users/marca/dev/git-repos/retools/docs/api/limiter.rst
Fix title underline too short in limiter.rst

Prevents warning:

    WARNING: Title underline too short.
Delete caching.rst

It's incomplete and it was causing this warning:

    retools/docs/caching.rst:: WARNING: document isn't included in any toctree
Merge pull request #35 from msabramo/eliminate_sphinx_warnings

Eliminate Sphinx warnings