Add metadata summary per FM-1523
(MODULES-1571) Add pending tests for facts
(MODULES-1571) TDD: Add new specs for facts

We're now using the Facter::Util::Resolution class, as it's easier to mock out and write specs for.

We're also checking against both Windows and non-windows environments
(MODULES-1571) Expand comment headers for facts

Using the format that's used in `puppetlabs-stdlib`
(MODULES-1571) Big refactor of `git_version`

Biggest change is it now just the version number not the whole string.

Before:
`facter git_version #=> 'git version 2.1.2'`
After:
`facter git_version #=> '2.1.2'`

It also now uses the Facter::Util::Resolution.exec so we can mock it out easier in specs
(MODULES-1571) change exec and html to use exec

This means we can mock and spec easier
Merge pull request #46 from petems/MODULES-1571-add_git_facts

MODULES-1571 Add Git Facts
Merge pull request #43 from laurenrother/master

Add metadata summary per FM-1523