Check to see if running on AppVeyor

Implements #146
- Reset AssemblyInfo.cs file back to initial values
- Added check, using APPVEYOR environment variable, to see if running on AppVeyor
  - Used this as basis: https://github.com/Particular/GitVersion/blob/a4b40aaec5a7bc1f9bb668fed5c4879dc36f8099/GitVersionCore/BuildServers/AppVeyor.cs
- General spacing changes around }'s