pre-process the ".." tokens before checking the filesystem

further fix to previous ast enhancement; dont log identifiers as "declared" once we're traversing inside functions since they are local to the function.

comments may contain quote characters [ticket:23]

  callable or list of callables which will be applied to the template text
  before lexing.  given the text as an argument, returns the new text.
- added mako.ext.preprocessors package, contains one preprocessor so far:
  'convert_comments', which will convert single # comments to the new ##
  format

- doc adjustments, changeset adjustments, modified unicode tests to
use ## instead of # for magic encoding comment.  # will still work for now.
- unsure whether we are going with #* *# or <%doc> for multiline comments,
looking like <%doc>.

changed around filtering so you can just say "decode.utf8" or "decode.<whatever>" for generic expression decoding

  immediately catch any encoding issues and ensure internal unicode
  representation.

  [ticket:16]
- cleanup in unit tests

- added "default_filters" argument to Template, TemplateLookup.  applies only to expressions,
gets prepended to "expression_filter" arg from <%page>.  defaults to ["unicode"], so that
all expressions get stringified into u'' by default (this is what Mako already does).
By setting to [], expressions are passed through raw.
- added "imports" argument to Template, TemplateLookup.  so you can predefine a list of
import statements at the top of the template.  can be used in conjunction with
default_filters.

magic encoding comment

file
- added modulename_callable to TemplateLookup to allow a function to determine module filenames
(takes filename, uri arguments).  used for [ticket:14]

with a template that indicates a non-standard encoding, are expanded into backslash-escaped
glyphs before being AST parsed [ticket:11]

converted to a list [ticket:9]