Address comments from @mikemcquaid.

1. Formatting fixes.
2. No more brew version of pypy,openssl,libxml2, and brew-pip. system versions will be used where needed
3. Install lxml Python module with install_args rather than with pip
4. add bin.env_script_all_files

NOTE:  Did not change the test because it is the simplest test. There is no "euca2ools" binary thus there is no euca2ools --version. euca2ools-version is a euca2ools command that is the equivalent.