[fixes #130] Changed ExecutionPolicy to Bypass to avoid failure.

It would appear combining the flags -ExecutionPolicy Unrestricted and
 -NonInteractive causes the following error;

Import-Module : File E:\Pester\Pester.psm1 cannot be loaded. The file
E:\Pester\Pester.psm1 is not digitally signed. The script will not execute
on the system. Please see "get-help about_signing" for more details..

See the following TechNet article for details on ExecutionPolicy settings;

http://technet.microsoft.com/en-us/library/hh849812.aspx