Supplement purescript-web3 with event parsing from block-interval

[kejace]

It is expected that we will want to "replay" the blockchain in order to not waste our time on generating events for consumption.

Suggested approach is to have an optional flag for a block-interval that purescript-web3 accepts as arguments, but other approaches are also welcome.

Please reference relevant issues on purescript-web3 as links here:

• Add the possibility to stream events purescript-web3#29