dev-tools should support option of using postgresql

[eggmaster]

This should allow for specification of postgresql username and password via environment variables, as well as configuration of the database name conductor will be using.

[cwolferh]

Breaking it into two steps:

1. The puppet scripts should be able to accept facter environment
   variables for an existing postgres database and configure conductor
   accordingly.

2. If the user specifies certain env vars, bootstrap.sh should install
   postgres (if needed) and create a new database (if desired), then set
   the appropriate facter vars before puppet gets invoked.

Focusing on the first step, I propose that when in "postgres mode"
puppet configures conductor based on the following env vars:

FACTER_POSTGRES_USERNAME  # typically just the current system user
FACTER_POSTGRES_PASSWORD
FACTER_POSTGRES_DBNAME

I think it is safe for the puppet scripts to assume the db is empty
(at least for now).

If FACTER_POSTGRES_DBNAME is not defined, puppet should configure
sqlite as it does currently.

Once the above is done, we can start step 2.

The following scripts may be useful for reference on postgres configuration:
https://gist.github.com/3178181#file_conductor_dev_root_prep.sh
https://gist.github.com/3178181#file_conductor_dev_setup.sh

[cwolferh]

Closing since this was addressed with #15 .