Added UTF-8 BOM (U+FEFF) to ps1-files

This is something that I forgot in my last PR (https://github.com/AnthonyMastrean/chocolateypackages/pull/27).
I didn’t do anything other than adding UTF-8 BOMs (byte order marks) to all ps1-files. This follows the [character encoding guidelines for Chocolatey packages](https://github.com/chocolatey/chocolatey/wiki/CreatePackages#character-encoding).

If you like to know why this is necessary, you can read these three interesting sources:
* https://en.wikipedia.org/wiki/UTF-8#Byte_order_mark
* https://en.wikipedia.org/wiki/Byte_order_mark#UTF-8
* http://www.w3.org/International/questions/qa-byte-order-mark.en.php?changelang=en#problems

Always keep in mind that UTF-8 BOMs aren’t a good thing. They should only be used with Microsoft products that require them.