Add a chocolatey installer

This adds a chocolatey installer for IsePester. For chocolatey users, cinst IsePester will install the latest Pester if they do not already have it as well as this module. It will put both in their ISE profile (creating one if it does not exist). So when they open ISE, they are good to go.

Doug: If you have chocolatey, invoking cpack in the repo will generate a .nupkg file. Then a cpush will deploy it to chocolatey. This PR makes both you and I "owners" of the package (you of course are listed as the single "Author"). If you do not want to create a chocolatey account, I can deploy it once you merge this in if you want.

I will be presenting on Unit Testing Powershell at the powershell summit on Monday and will be demonstrating how to use this to debug tests. I'd love to have this setup by then so i can give instructions to use chocolatey which i think will make it much easier to setup.

Thanks!