allow installation exception to be caught in InstallCommand
added -p option to mkdir in build.sh to prevent failure when exists
Merge pull request #797 from adamralph/779

added -p option to mkdir in build.sh to prevent failure when exists
Merge pull request #796 from adamralph/794

Fix for #794 - failed installation yields exit code 1
Updated tests to fail
Added fetching of framework assemblies from nuget packages
Merge pull request #801 from khellang/framework-assemblies

Reference framework assemblies specified in installed NuGet packages
Fixed failing tests
red: added RoslynScriptEngineTests.ShouldAllowUseOfScriptHostExtensionMethods to demonstrate that extension methods on script host do not work