Install newer Boost PPA to support newer HHVM versions.

See: https://github.com/facebook/hhvm/wiki/Prebuilt-Packages-on-Ubuntu-12.04
Via: https://github.com/facebook/hhvm/issues/2039
admin_password was being passed as admin_email. Oops.
HHVM 3.0 uses server.ini, not server.hdf