added a function to censor passwords and updated HACKING.txt

[samghelms]

I love this package, but it keeps printing out my password in cleartext when I use it with an odbc driver. For example:

input cell:

%%sql
select * from csn_survey.tblSurvey limit 3

output:

* vertica+pyodbc:///?odbc_connect=DRIVER=/opt/vertica/lib64/libverticaodbc.so;SERVER=myvertica.com;DATABASE=mydb;PORT=myport;UID=samghelms;PWD=mypassword

<table output>

This PR adds a censor_passwords function that attempts to find any password parameters in the URL string and censor them.