Add postgresql configuration support

Install dependencies for either sqlite or postgresql based on value
of FACTER_RDBMS

Add postgresql install steps to bootstrap.sh, template for database.pg
to puppet templates, puppet step to run rake db:create:all

Make postgresql the default RDBMS selection.
Merge pull request #15 from eggmaster/postgresql-work

Postgres support in bootstrap.sh.  Postgres now the default but it is still possible to use sqlite.
First attempt to only need one yum install.

(untested, probably needs work)
Now with 100% more "actually works". :)
Only run yum install if there are packages to install.
Add sqlite-devel dependency for Deltacloud master branch.
Merge pull request #16 from justinclift/yumstreamline

Streamline yum usage (one yum install command instead of multiple).
A sudo-enabled ubuntu user may now use system ruby

Prior to this commit, ubuntu users had to use rbenv.  Now, as was
already the case with rhel6/fc16/fc17, a sudo-enabled user may instead
use system ruby.
Merge pull request #19 from cwolferh/ubuntu_sysruby

A sudo-enabled ubuntu user may now use system ruby
Allow checking out of any project tags or commit hashes

Prior to this commit, could only checkout branches by name.  Now, env
variables such as export FACTER_CONDUCTOR_BRANCH may specify a branch,
tag or commit hash.
Tim support

Builds and starts up conductor cleanly, pointing to a local source
checkout of tim/master.
Merge pull request #21 from cwolferh/allow_git_checkout_tags

Allow checking out of any project tags or commit hashes
Merge remote branch 'upstream/master'