Read the packages repository path from $ENV:APPDATA\NuGet (if it exists). Resolves #159
Delete temp files when disposed.

In 61b3aaa5757ef1768ac8ed73122473020c66d9a8, WithTempDirectory was changed
to defer its actions; this left all the temp files on the disk when
running tests.
Remove unnecessary Path.Combine.

file and dir are already absolute paths.
Fix temp paths.

The path 'ShimmerDesktopDemo' is hard-coded in 'InstalledSquirrelDesktopDemo-1.0.0.zip'.
Merge pull request #223 from LogosBible/fix-with-temp-directory

Fix WithTempDirectory
Close files before deleting.

The stream from File.OpenRead was not being disposed, causing a potential sharing violation when the temp folder was deleted at the end of the test.
Fix tests that do care about the package directory.
Merge pull request #207 from peters/master

Read the packages repository path from $ENV:APPDATA\NuGet (if it exists)...
Merge pull request #224 from LogosBible/fix-unit-tests

Fix unit tests