add Manpages

- add bats.1
- add bats.7
- tweak install.sh to install manpages
Update the man pages
Add makefile for man pages
Ensure $PREFIX/share/man/man{1,7} directories exist

Fixes #33
Merge remote branch 'upstream/master'
Modified the `run` command to take a `-v` flag for preserving variables from a run.