Add suspend version of composing functions

[pablisco]

As mentioned in arrow-kt/arrow-fx#199 (comment) we can move the andThen function to composition.kt and then (pun half intended) make arrow-fx-coroutines depend on arrow-syntax.

This may require some investigations as currently suspend is not taken into account when doing overload of functions:
https://youtrack.jetbrains.com/issue/KT-23610

We may require to have a different @JvmName or altogether (i.e. andThenEffect).

We could also include these other permutations:

• suspend fun andThen fun -> suspend fun
• fun andThen fun -> suspend fun

As well as for other functions in composition.kt