(#172) Altered way that GitVersion is installed

- Rather than have GitVersion.exe in the Tools folder, lets install it as part of build process
- Deleted GitVersion.exe from Tools folder
(#172) Change installation source for GitVersion

- Temporarily use the hooky installation source for GitVersion which comes from my MyGet feed
- This has the result of Pull Request https://github.com/Particular/GitVersion/pull/262
(#172) Removed artifact publishing from yml file

- This will instead be done within the psake build script
(#172) Added nuget package caching

- Now that the Pull Request issues in AppVeyor have been correct, we can add back in the nuget package caching, which should speed up the build somewhat.
(#172) Completed GitVersion, added StyleCop and CodeAnalysis

- When running in AppVeyor, run GitVersion with /output buildserver and read environment variable to get LegacySemVer version number
- When not running in AppVeyor, call GitVersion directly, and parse the JOSN output to get the LegacySemVer version number
- Added Analysis of StyleCop Errors, and publishing of StyleCop report
- Added Analysis of Code Analysis Errors, and publishing of Code Analysis report
(#172) Switch to using REST API in AppVeyor

- As a result of discussions in this PR
	https://github.com/Particular/GitVersion/pull/262
- Changed to make use of a new REST API method in AppVeyor to set environment variables which are then immediately available in the running process.
- This means that we no longer have to call GitVersion twice
(#172) Changed to official source for GitVersion

With the release of 1.3.2 of GitVersion, I shouldn't need to use my manually compiled version anymore.
(#172) Added XSL Transform of StyleCop and FxCop

- Using a basic XSL Transform script, and some sample XSL Files, applied a tranform to the XML report files, so they are easier to view
- Added check to decide whether these needs to be published as an artifact when running on AppVeyor