Changes in v2.18

Reversed a change introduced in the 2.17 release that disabled shared compilation for Roslyn builds.  
Although it seemed like a good idea at the time, this change had a significant impact on build times under 
VS2015.

Introduced a speculative fix to try to resolve issues where NCrunch would fail to correctly load all cached 
data under VS2015.

Fixed an issue where workspace errors being kicked up on grid nodes were causing the engine to hang.

Fixed IgnoreAttribute not working for TestCase and TestCaseSource under NUnit3.

Disabled NUnit3's internal parallelization features, as these were causing NCrunch to misinterpret test 
results and explode inside the test environment.

Fixed an issue where NCrunch was triggering NUnit2 to execute SetUpFixtures without any consideration of 
targeted namespaces.

Fixed a race condition in which the NUnit3 adapter could hang a test run when the last fixture executed in 
the run timed out.

Added extra information to file locking error messages.