Re-add variables.less

At one time we were generating a LESS file containing all of the
configuration needed for Bootstrap to work, thus removing the need
for the variables.less file included in Bootstrap.  Now, we are
allowing themes to define a set of variables that they want to
customize.  This set of variables is disjoint from the Bootstrap
variables.  Thus we need to include the Bootstrap variables.
Fix error in ESPUser.__init__()

I saw this on one of my VM dev servers with Ubuntu 13.04.  It said
that the value assigned to a method __name__ attribute had to be
a string, and it was possible for a Unicode object to be passed in.
I'm not sure why we didn't see this before, but the change should
be pretty inconsequential.
Avoid path hacking via os.path.join
Switch from using 'node' binary to 'nodejs'

Our production servers and most dev servers are using Ubuntu, and on
Ubuntu machines the NodeJS binary is named 'nodejs'.  For some reason,
on my Windows dev server it is called 'node', so the code I was using
wouldn't work on Ubuntu.