in dev mode, concatenate scripts instead of minifying

faster reboot & restores sanity to those trying to debug browser
specific issues on IE and FF. not that you have much sanity to begin
with if it's an IE bug...
until now, this variable was never false... so I'm just removing it

@julianlam just in case
Merge branch 'master' of https://github.com/NodeBB/NodeBB