Reduce volume of Travis build output

Hundreds of lines of build output passed through Travis JS parsing bring
my browser (at least) to its knees - little of it is interesting or even
relevant, keeping the last 40 lines of stdout for most make targets is
plenty (we keep all of stderr).
Test some management commands

This is far from complete, but may catch some regressions
Require Jinja2 < 2.7 for Python 2.5

Jinja2 is a requirement of Sphinx (used to build documentation), but the
latest (2.7) version requires Python 2.6; allow build to succeed by force
installing older 2.6 version before processing requirements