Updated TortoiseGit to 1.8.12.0

Hi,

I just updated TortoiseGit to the latest 1.8.12.0.
`TortoiseGit.nuspec` is also in UTF-8 without BOM now so we follow the [Chocolatey Guideline](https://github.com/chocolatey/chocolatey/wiki/CreatePackages#character-encoding). That should explain the non-version related changes.

I've tested it on my own machine : Windows 7 x64. It worked just as before : it stopped `explorer.exe` (and `chrome.exe`) without rebooting.

Thanks for all the packages by the way !