Using host Linux (Ubuntu 12.04); performance was abysmal.

On initial load of localhost:4000, the http calls for
additional Javascript files via the browser appears to take
more than a few minutes with *.js endpoints loading in one
file at a time very slowly.

It was observed that the Ruby process was consistently
pegged at 95% and up.  This behaviour is not observed
using a Mac OSX.

However, adding a single core to the guest OS
(from 1 to 2) improved performance considerably.

The patch detects if the host system is Mac OSX or
Linux and attempts to assign the same number of cores
as is present on the host.

Vagrantfile

@@ -19,6 +19,21 @@ Vagrant.configure("2") do |config|
     # This setting gives the VM 1024MB of RAM instead of the default 384.
     v.customize ["modifyvm", :id, "--memory", [ENV['DISCOURSE_VM_MEM'].to_i, 1024].max]
 
+    # Who has a single core cpu these days anyways?
+    cpu_count = 2
+
+    # Determine the available cores in host system.
+    # This mostly helps on linux, but it couldn't hurt on MacOSX.
+    if RUBY_PLATFORM =~ /linux/
+      cpu_count = `nproc`.to_i
+    elsif RUBY_PLATFORM =~ /darwin/
+      cpu_count = `sysctl -n hw.ncpu`.to_i
+    end
+
+    # Assign additional cores to the guest OS.
+    v.customize ["modifyvm", :id, "--cpus", cpu_count]
+    v.customize ["modifyvm", :id, "--ioapic", "on"]
+
     # This setting makes it so that network access from inside the vagrant guest
     # is able to resolve DNS using the hosts VPN connection.
     v.customize ["modifyvm", :id, "--natdnshostresolver1", "on"]