Loosen filter regexes slightly

to catch a few messages that slipped through when I was installing
docutils on Python 3.4:

    warning: no files found matching 'MANIFEST'
    warning: no previously-included files matching '.cvsignore' found under directory '*'
    Skipping implicit fixer: buffer

Before:

    $ pip install ~/src/docutils --upgrade
    Processing /Users/marca/src/docutils
        warning: no files found matching 'MANIFEST'
        warning: no previously-included files matching '.cvsignore' found under directory '*'
        warning: no previously-included files matching '*~' found under directory '*'
        warning: no previously-included files matching '.DS_Store' found under directory '*'
    Installing collected packages: docutils
      Found existing installation: docutils 0.13
        Uninstalling docutils:
          Successfully uninstalled docutils
      Running setup.py install for docutils
        Skipping implicit fixer: buffer
        Skipping implicit fixer: idioms
        Skipping implicit fixer: set_literal
        Skipping implicit fixer: ws_comma
      ...

After:

    $ pip install ~/src/docutils --upgrade
    Processing /Users/marca/src/docutils
    Installing collected packages: docutils
      Found existing installation: docutils 0.13
        Uninstalling docutils:
          Successfully uninstalled docutils
      Running setup.py install for docutils
      ...
Merge pull request #2201 from msabramo/filter_out_a_couple_more_warnings

Loosen filter regexes slightly