Fixes Squirrel/Squirrel.Windows#67
Changed from LastOrDefault() to Last()
Automatically download and install .NET 4.5 if necessary
Disable creating a NuGet package of the test suite because lolnuget
Give the download progress callback class a more descriptive name
Merge remote-tracking PR #103
Clean up error handling in FxHelper
Add some more tests around checking for updates, esp. in easy mode
If we fail to check for updates, returning a dummy update is insanity
Merge remote-tracking branch 'origin/pr/114'
Update.exe being Squirrel-aware opts people into Squirrel events. Closes #107
Version bump to 0.6.0
Omg.