Update README to avoid mynt gen error

Step 4 (pip install -r requirements.txt) implies that the user is at the root
of the repo. However, mynt gen must run from ./www to avoid
'jinja2.exceptions.TemplateNotFound: site.html' occurring because
_templates moved into ./www during the redesign.
removed old ATX location folder at root
add title block to base template so locations can easily override titles

e.g. "PyLadies ATX" instead of just "PyLadies"
Add template blocks to site.html to give children more control

Wrapped some sections of main site.html in template blocks to give inheriting
pages more customization options: e.g., location-specific pages can modify the
sidebar to display meetup info, tweets specific to their locale.
Modify meetup widget to allow for localized use

addUpcomingMeetups() now takes meetup chapter ID(s) as an argument, so local
groups can use the widget to show only nearby upcoming events, etc. Edited
site.html template to use chapter_ids with updated addUpcomingMeetups().
Create PyLadiesATX local page

Meetup widget shows only Austin events. Footer links go to localized
destinations (Google+ profile, Github org page, etc). "Blog" generated from
Meetup mailing list feed. Removed mailing list sign up box and added "Join Our
Meetup" button. Sponsor button goes to PyLadiesATX sponsor page.