Handle TERM, QUIT and ABRT signals

Gracefully exit child processes in the case one of the above signals is
received.
Merge pull request #4 from benjamin-surma/master

Handle TERM, QUIT and ABRT signals
test-framework -t switch support

Requires test-framework 0.8.0.3
(Thanks to Bryan O'Sullivan for merging the changes making this
possible!)
Merge pull request #5 from benjamin-surma/test-framework_exclusion_support

test-framework -t switch support
Fixed license information
Removed useless pragma
sandboxTests API change

This removes the need to setup a dummy sandboxTestGroup for most cases.
Merge pull request #6 from benjamin-surma/master

test-framework-sandbox improvements
[test-sandbox] Version 0.0.1.4
[test-sandbox-quickcheck] Version 0.0.1.3
[test-sandbox-hunit] Version 0.0.1.3
[test-framework-sandbox] Version 0.0.2.0
Migration from StateT to ReaderT + IORef

This change was made to easily handle cases with asynchronous exceptions
arising in IO sections of the code.
This allows access to the latest state even in exception handlers.
Merge pull request #7 from benjamin-surma/ioref_migration

Migration from StateT to ReaderT + IORef
Delete experimental (and unused) test-sandbox-expect
[test-sandbox] Version 0.0.1.5
[test-sandbox-hunit] Version 0.0.1.4
[test-sandbox-quickcheck] Version 0.0.1.4
[test-framework-sandbox] Version 0.0.2.1
Code cleaning and memory usage optimization

Now that the sandbox' state is reliable, we can use bracket and finally
from Control.Exception.Lifted with no issues.
In Test.Framework.Providers.Sandbox(sandboxTests), there is no need for
a dedicated cleaning dummy test anymore for the same reasons.