Fixes #195: Respond from any domain

If the current domain (HTTP_HOST) isn't registered on the site,
assume we want to access blog_id = 1.
Add inline comments to explain why we're setting the blog ID manually.
Additional url hacks to support arbitrary domains

In server environments (QS AMI), need to allow accessing the site on a
domain other than the one initially installed (vip.dev)

Fixes #195
Fix equality check in domain hack
Merge pull request #198 from nickdaugherty/issue-195

Additional url hacks to support arbitrary domains
Merge pull request #196 from Automattic/issue-195

Fixes #195: Respond from any domain