0.5.1: Merge pull request #9 from karmarama/bugfix/retainCycles

Fixed retain cycles

0.5.0: Merge pull request #8 from timsearle/relay

Modifying Relay to not have a historical value storage

0.4.0: Merge pull request #7 from timsearle/ignoring-duplicates

Added ignoringDuplicates function

0.3.0: Merge pull request #4 from timsearle/initial-value

`initial`

0.2.0: Merge pull request #3 from timsearle/reduce-and-tests

Adding `reduce`