Minor requirements cleanup

Remove unused django-bcrypt and its dependencies.

Update Django version in requirements.txt to 1.4.5 with explanatory
comment.

Add instruction to installation docs to install dev requirements after
compiled requirements.
Merge pull request #1158 from jgmize/minor-requirements-cleanup

Minor requirements cleanup
Fix Bug 903089 - robots.txt changes

In production, add the following line to robots.txt:

disallow: /*/newsletter/existing/*

In dev, staging, etc:

user-agent: *
disallow: *

settings.SITE_URL is used to determine if we are in production.

In etc/httpd/global.conf, add a RewriteRule to serve robots.txt from
Django.

Add robots.txt to settings.SUPPORTED_NONLOCALES to eliminate redirect.
Merge pull request #1156 from jgmize/bug-903089-newsletter-robots

Fix Bug 903089 - robots.txt changes