Updated content to conform to README best practices template

Before alterations, this content was the module author-determined
description of and instructions for use of the module.

As part of a joint Forge/Docs team effort to standardize formatting and
encourage quality module documentation, a best practices README
template was created via internal and external user testing. That
template was then applied to this module.

I pulled in content from the original README on GitHub and the Module
of the Week blog post. A table of contents was added for navigability,
standard headings were added (Overview, Module Description, Setup,
Usage, Implementation, etc.) to organize content, existent and
pulled-in content was moved under its appropriate heading and edited
for tone/flow/clarity, links to outside documentation were updated, and
basic formatting was done to adhere to template standards.
Fixed typos, rewording and typsetting per feedback

Updated spelling errors, typsetting issues and some wording suggestions
based on module author feedback
Update postgres_default_version to 9.1 for debian 7.0

/etc/debian_version on Wheezy was updated to 7.0 with the release of the
base-files package on 2012-12-12, which means that wheezy could be
either 7.0 or wheezy depending on what version of base-files is
installed. To handle both cases we treat 'wheezy' and '7.*' as
synonymous.
Merge pull request #94 from puppetlabs-operations/wheezy_7_0_default_version

Update postgres_default_version to 9.1 for debian 7.0
Merge pull request #89 from laurenrother/master

Updated content to conform to README best practices template
Added support for tablespaces
Tablespacing improvements
Update spec/README.md
Improved tablespace rspec test
Final commit for 2.0.1 release; update CHANGELOG and Modulefile
Merge pull request #100 from kbrezina/master

Support for tablespaces
typo fix in example
Merge pull request #104 from boinger/master

Minor typo fix in README