Introduce a vvv-hosts.dat file in the www directory to handle default domains.

The code in place already handles this along with subdirectories of www, so we should take advantage of it to make the Vagrantfile a bit less confusing.

It would be nice if if our `.dat` files could have comments in them that don't cause trouble with the output.
Additional documentation in Vagrantfile around the vvv-hosts.dat process
Update provision.sh to handle default and custom vvv-hosts.data files.

Was having trouble getting the existing stuff in provision.sh to process all the vvv-hosts.dat files, so I went with a while loop instead, reading the output of the find command as if it was a file. This now checks to see if an exact match already exists before adding it to the hosts file, lest we end up with a huge file after a bunch of provisions.

I don't understand all of the magic, but there's some fanciness in line 507 that allows it to read each line and ignore empty lines.

Also clarifies a few things in the comments and adds some output to the provisioning explaining what domains were added and from what hosts files.
Modify provision.sh to support comments in vvv-hosts.data file

If the first character of a line begins with a #, then we can safely skip it as a comment.
Split vvv-hosts.data on newline rather than on space.

IMO, this enforces a more readable file *and* allows us to work toward comment support in the file, something that I'd like to include as it has been fairly important for the VVV project as a whole so far.
Modify Vagrantfile to ignore lines starting with # when parsing vvv-hosts.dat

This allows us to comment the crap out of our vvv-hosts.dat files. :)
Add documentation to the vvv-hosts.dat file explaining its existence.
Merge pull request #1 from jeremyfelt/auto-site-tweaks

Additional tweaks to @simonwheatley's PR of @westonruter's PR of VVV