- fix broken py2k/py3k isms

standalone gendered pronoun with a gender-neutral subject, but also
have replaced all occurences of "his/her", "his or her", etc.  The docs have always
strived to account for both genders in any non-specific singular pronoun,
however recent controversy in the community suggests
that a zero-gendered-pronoun policy is probably best going forward.

to allow ad-hoc display of the source of any file, as well as a "directory listing" structure.
- reorganize examples/ to take advantage of new extension.  in particular, keep moving all
the descriptive text for files etc. into module docstrings, taking more advantage of
self-documentation.

of SQL cache keys wasn't applying deduping labels to the
statement the same way :class:`.Query` normally does.

- went through examples/ and cleaned out excess list() calls

the limit/offset parameter values wouldn't be taken into
account when computing the cache key.  The
_key_from_query() function has been simplified to work
directly from the final compiled statement in order to get
at both the full statement as well as the fully processed
parameter list.

which was due to the change in #2614.