Update buildtools to version 1.0.14-prerelease
Merge pull request #182 from FiveTimesTheFun/buildtools-14

Update buildtools to version 1.0.14-prerelease
Remove AllowUnsafeBlocks as it's no longer needed
Make immutable collection tests portable
Remove commented out code (responding to PR feedback)
Merge pull request #183 from nguerrera/portable-immutable-tests

Make immutable collection tests portable
Remove unused file: PinnedImmutableArrayTests.cs

The PinnedImmutableArray class no longer exists, but the tests for it
sitting in the tree without being pulled in to the .csproj.
Merge pull request #184 from nguerrera/remove-unused-immutable-file

Remove unused file: PinnedImmutableArrayTests.cs