fix missing mods directory that breaks installation+issues

Webrick / Passenger fail with

local/mods directory not found

If I create this directory ( /var/local/wagn/local/mods ) manually, wagn (running through passenger and Apache) fails with a Hitch! 500.

I understand it is indeed for local mods, not a path problem.

I used the default setup instructions, and cloned wagn from GitHub yesterday.

Ruby version is 1.9.3

Wagn version is 1.12.5

Running on OpenVZ'ed Debian 7.0