BF: try debugging installer failure

Also - fix directory for running tests.
MAINT: add .travis.sh to .gitignore

.travis.sh generated from .travis.yml by terryfy/travis2sh
RF: refactor Makefile to use env vars

Use GNU make extensions to get Python version and get-pip.py path from
environment variables.

It is fun trying to work out Makefile syntax with no internet access and
no Makefile manual.
TST: do pip install more manually for debugging

Try doing the pip install with pip commands after running the installer
do see if we can get a better error message.