password reset tool
Don't try to update password if we don't have one.
Make it not be misleading if you don't specify a password.
Documentation improvements.
Merge branch 'master' of github.com:tidepool-org/tools into kjq/pwreset
Turn off echo for --input and deal with empty passwords.
Merge pull request #6 from tidepool-org/kjq/pwreset

Tool has been deployed and tested by me and others, so I'm merging.