Support the forms listed by the W3C [1]. I also removed the
'%Y-%d-%m' form, which can be confused with the '%Y-%m-%d' ISO form.
The new ISO forms can use 'Z' to designate UTC or '[+-]HHMM' to
specify offsets from UTC. Other time zone designators are not
supported.
The '%z' directive has only been supported since Python 3.2 [2], so if
you're running Pelican on Python 2.7, you're stuck with 'Z' for UTC.
Conveniently, we get ValueErrors for both invalid directives and
data/format missmatches, so we don't need special handling for the 2.7
case inside get_date().
[1]: http://www.w3.org/TR/NOTE-datetime
[2]: http://bugs.python.org/issue6641
Do not use abbreviated locale versions of month/whatever, because it seems that
this is not standard (e.g. MacOS abbreviating differently than GNU/Linux).
The old get_relative_path() implementation assumed os.sep == '/',
which doesn't hold on MS Windows. The new implementation uses
split_all() for a more general component count.
I added path_to_url(), because the:
'/'.join(split_all(path))
idiom was showing up in a number of cases, and it's easier to
understand what's going on when that reads:
path_to_url(path)
This will fix a number of places where I think paths and URLs were
conflated, and should improve MS Windows support.
