(#11276) Add minitar for Windows

This commit adds minitar so that the module tool will work on Windows.
(#11276) Install GeoTrust Global CA on Windows

In my local Windows VM, it was not able to connect to the production or
pmtacceptance forge due to the GeoTrust Global CA cert not being present
in my Root certificate store.

This commit adds a `git` setup step that installs the certificate on
Windows. When executed, the step installs the following cert:

  CN=GeoTrust Global CA, O=GeoTrust Inc., C=US

If the cert is already present, the `certutil` command still returns 0,
so no special `acceptable_exit_code` logic is required.
Merge pull request #427 from joshcooper/minitar

Minitar
Specify the behavior we want in tests and documentation

whitespace fixup
Use YARD better
Move helpers for the dsl into a DSL namespace
outline how we should be requiring subsystems
Use SimpleCov if not on Ruby 1.8 & update Rakefile
Test DSL/Assertions
Document and test DSL/InstallUtils
Document and test DSL/Outcomes
Document and test DSL/Roles
Split PuppetCommands into Helpers and Wrappers

Move much of TestCase into Helpers

Refactor Command

Document and test Helpers,Wrappers,TestCase,Command
Add Documenting guide
Improve `require`s for use as a library
Do not install markdown by default on 1.8 (Regression)
Improve .gitignore with documentation and bundler artifacts
Add documentation tasks
Finalize Documentation for this pass