Use bash, not sh for install scritps

Install scripts don't work in pure sh; they may work on some systems where
the /bin/sh binary actually implements more than the pure Bourne Shell but
fail on other ones (e.g. Ubuntu).

Just using bash works.
Merge pull request #450 from mzgol/install-script

Use bash, not sh for install scritps
Oxford comma
Following http://www.shellcheck.net advice
wip