Update ssh-and-http documentation to remove some unnecessary steps and add a required variable

The documentation on the ssh-and-http page is slightly incorrect.  A HTTP_ANON_USER variable is required in order to function, or else one gets this error:

[root@boris ~]# git clone http://git1.dmz.scl3.mozilla.com/git/testing.git
Cloning into 'testing'...
fatal: remote error: FATAL: invalid user ''

Additionally, with apache's ScriptAlias line, a '/var/www/git' directory is no longer required, so I removed references to that to make the documentation simpler.

I was also considering removing the $ENV{PATH}="newstuff" line reference because I got it working without that line, but I'm not sure if I will see unforeseen breakage because of it in the future.