Cleaned up docstrings in vexflow/base.py:

    - indented all code blocks with "::",
    - split code blocks after any interpreter output,
    - capitalized all sentences in function and class docstrings,
    - added sentence ending punctuation ('.', as well as ':' when introducing
      code blocks),
    - and added `backticks` around some previously unquoted code references.

Another pass of proofreading is necessary to get the rest of the module-level
variable definitions, as well as to apply backticks to the remaining code
references.


git-svn-id: http://music21.googlecode.com/svn/trunk@3475 5c16147e-a200-11de-b0cc-ab0ad15e60d0