Support asserting suspend function

[ychescale9]

Resolves #151.

This PR adds support for asserting suspend function invocation.

Sample usage:

@Test
fun testASuspendFunctionThatThrowsTheExpectedException() = runBlockingTest {
    suspend fun func() {
        suspendCancellableCoroutine<Any> { throw IndexOutOfBoundsException() }
    }
    invokingSuspend {
        func()
    } shouldThrow IndexOutOfBoundsException::class
}

• invokingSuspend is the new API added that takes a suspend function as parameter.
• runBlockingTest is an experimental API from kotlinx-coroutines-test which provides a CoroutineScope as a lambda. In this case runBlocking also works.
• PR adds the kotlinx-coroutines-test dependency only for testing and no new runtime dependency is included in the library itself.

Checklist

• I've added my name to the AUTHORS file, if it wasn't already present.

[ychescale9]

@MarkusAmshove invokingSuspend sounds a bit verbose to me. MockK for example adds a co prefix to all the coroutine version of the APIs so in our case it would be coInvoking. But it's also a bit different since we don't really depend on any of the coroutines libraries. What do you think?

[MarkusAmshove]

Thanks for the PR and also updating the docs!
The implementation looks good and I'm willing to merge it, but since you asked about the naming I think I'm with you on the coInvoking.

I'm in favor of either invokeSuspending or coInvoking, since the ing form reads better with e.g. shouldThrow.

I'm fine with both, so I'll let you decide :-)

[ychescale9]

Renamed to coInvoking 😃