Added timezone prompt to quickstart

This implements one of the improvements suggested in Issue no: #1337.
Asks user for timezone during the quickstart process.
It also validates input time zones by checking if they exist in the pytz.all_timezones list
(white-space and case insensitive)


Lower case version of the tz timezone list
Note: 'str.lower' is used instead of 'str_compat.lower'
Reason:  in Py2 the pytz.all_timezones is a list of 'str's, so 'unicode.lower' cannot be applied and in Py3 of course everything is str. So this makes it work on both