Remove setting of PS1 from awsenv
 - better to add something to .bash_prompt that includes $AWSUSER in PS1
Switch all shebangs to #!/usr/bin/env python
Merge pull request #35 from yo61/feature/fix_aws_env_ps1

Remove setting of PS1 from awsenv.
Should never really have committed awsenv in its original form :)
Merge pull request #40 from yo61/feature/rb_gh39_fix_shebang

Feature/rb gh39 fix shebang.
thx robin.