* Add more functionality to the sim (#5)

* backends: implement more of ethclient in sim

* backends: add BlockByNumber to simulated backend

* backends: make simulated progress function agree with syncprogress interface for client

* backends: add more tests

* backends: add more comments

* backends: fix sim for index in tx and add tests

* backends: add lock back to estimategas

* backends: goimports

* backends: go ci lint

* Add more functionality to the sim (#5)

* backends: implement more of ethclient in sim

* backends: add BlockByNumber to simulated backend

* backends: make simulated progress function agree with syncprogress interface for client

* backends: add more tests

* backends: add more comments

* backends: fix sim for index in tx and add tests

* backends: add lock back to estimategas

* backends: goimports

* backends: go ci lint

* assert errs