Make linting checks part of the development process

[adrianbrink]

We should strive to only have very clean code for ethermint.

We currently have two separate linters gometalinter and megacheck.

As such this issue is three fold:

1. Add an explanation of how to install all our linters.
2. Update the Makefile so that the linters get run on every test and build run.
3. Update the CI build steps to fail on linting errors.

[rigelrozanski]

This should not be specific to ethermint, needs to be streamlined with tendermint coding standards/practices... here https://github.com/tendermint/coding/blob/master/go/coding_standard.md#linters
But also https://github.com/tendermint/coding/

Maybe sync up with @zramsay on this end for the documentation, I know zach has been modifying and organizing the coding repo

[zramsay]

I'm assigning myself to tackle the standard (rather then implementation). On points 1 & 2 i think we should just list those standards/explanations/Makefile examples in the coding repo - otherwise every new "major" repo is going to go through the same issues repeatedly.

[adrianbrink]

Please check https://github.com/tendermint/ethermint/blob/develop/Makefile#L69 to see which linters are running. I've mostly fixed up ethermint that those pass.