Fix install_instructions

exec_vagrant calling install_instructions would raise a NameError
Add Windows Support

ENV[PATH] uses a different separator on Windows, and of course a
different install location for Vagrant.
Skip a rubygems vagrant-wrapper wrapper

Rubygems creates a wrapper named 'vagrant' that executes our own 'vagrant' wrapper,
so we need to make sure we skip that too.
Add specs for Windows code, clean up

This gets the specs passing on my Ubuntu workstation, provided vagrant is installed.
Upgrade tests to Rspec3 syntax
Look for vagrant.exe on windows

The File.executable? check looks at specific files, but Windows
tends to treat "vagrant" the same as "vagrant.exe"

There's also a bash script shipping as bin/vagrant on Windows.
I'm mostly ignoring that.
Shorten helper methods

Take @tknerr's advice on shortening helper methods, but use !! to still
return a boolean value.
Include mingw/git bash path to default Windows install of Vagrant
Update vagrant_bin unit tests to work on Windows
Fix test regex to make .exe optional
Fix misnamed tests

While cleaning up tests for rspec3 I misnamed some of them. Fixed.
Remove unnecessary !! operator
Fix integration tests without gem

The integration tests require the gem to be installed, this catches that
case and tries to add the appropriate directory.
Merge branch 'btm-windows'
Updated .gitignore
Updated gemspec to reflect RSpec3 testing updates.
Improved version parsing to avoid matching "I18n.enforce_available_locales" deprecation warning in tests against the old Vagrant Gem.
Updated README and moved background info to ENIGMA.md
Release version 2.0