Documented upstream_error event
Rework .travis.yml to work with new build env

Use new-build 64 bit packages
Test as unprivileged user due to lack of cpanm as root
Chmod /var/log/openresty dir before test to avoid permission issues
Call /opt/openresty/sbin/openresty directly to avoid $PATH problems
Remove `which openresty` since binary is not in path anyway now
Fix packages with apt to make sure package deps are installed

Signed-off-by: Ben Agricola <bagricola@squiz.co.uk>
Merge pull request #59 from benagricola/fixing_travis

Rework .travis.yml to work with new build env