Use .getEnv() instead of NODE_ENV

Hello @dpup, 

Currently in matador we rely on ``NODE_ENV || 'development'`` in some
places and, in others, use only ``NODE_ENV``. This pull request
makes sure we always rely on only one source of truth for current
environment.

This fixes a bug that, when running the server with no specified NODE_ENV,
nothing in the 'development' configure call gets executed (and thus,
soy templates are not automatically recompiled and there is no request
logging).

Please review the following commits I made in branch 'vinny-node-env'.

85591f724fb8d4c8ac1581526fe1a31fa275d78a (2013-07-29 10:04:58 -0700)
One source of truth for current environment


R=@dpup