Support plv8 version number discovery about plv8 HOT 4 CLOSED

Can you explain more specifically what you want to do it by knowing its version?

1)  I want to automate the installation/upgrading of plv8 via my install 
scripts (for an application).
2)  We just had an issue where the code was working in dev but not on our 
servers (production) and didn't have a quick way of finding out the version of 
plv8 on the server.

What about something like:

if (plv8.version >= '1.1.0beta1'){
  plv8.execute('SELECT ... ');
}else{
  plv8.elog(ERORR, '1.1.0beta1 required');
}

Commit 0763b6 addresses this.