first pass at getting atom feed working.

Related to issue #34
Changes to atom feed in response to comments from Mr0grog

issue #34

Conflicts:
	app.py
updated example configuration file to add ATOM_SIZE

issue #34
Use background-image instead of background shorthand to specify replacement images for retina screens. Fixes #59.
Merge pull request #60 from codeforamerica/bug-59-retina-images

Fix improperly sized retina images in Chrome
made minor tweaks

doing this with the github webeditor, we will see how this goes.
tweaked default ATOM_SIZE
Merge branch 'atom_rb' of github.com:tacaswell/srtracker into tacaswell-atom_rb
Move Werkzeug imports up above user-code imports.
Link atom feed from recent SRs page.
Merge branch 'main_page_pagation' of github.com:tacaswell/srtracker into tacaswell-main_page_pagination

Conflicts:
	app.py
Add SRS_PAGE_SIZE to env-based configuration
Only do paging when SRS_PAGE_SIZE is set. Otherwise continue with the older, more standards-ish behavior.
Merge branch 'main_page_pagination' into sr_code_filter

Conflicts:
	app.py
	templates/index.html