Make certifiers stand alone

[ethanfrey]

I want to create a stand-alone, minimal, and clean certifiers package, which can be moved into tendermint core. After merging this in and updating dependencies, in the future one would just have to replace:

import "github.com/tendermint/light-client/certifiers"

with

import "github.com/tendermint/tendermint/certifiers"

The proofs directory needs cleanup as well, and then would move into cosmos-sdk, rendering this repo deprecated.

TODO:

• [x] Move all code from light-client into certifiers or proofs
• [x] certifiers depends only on the following tendermint repos: tendermint/tendermint, abci, go-crypto, go-wire and tmlibs
• [x] all code compiles and tests pass
• [x] nice godocs
• [x] code cleanup

[ethanfrey]

Lots of name changes, unneeded public methods made private, etc...

Please checkout and run local godoc and look at http://localhost:6060/pkg/github.com/tendermint/light-client/certifiers/ before looking at the code itself. That should be the high-level intro and be usable.

Functionality is the same as before and has been tested and reviewed in other prs.

[ebuchman]

Please checkout and run local godoc and look at http://localhost:6060/pkg/github.com/tendermint/light-client/certifiers/ before looking at the code itself. That should be the high-level intro and be usable.

Fantastic.

[ethanfrey]

I would just copy it into tendermint/certifiers, and quickly update the import path. We don't have to have this in by 0.12, but it would be nice, even if this PR is pending other cosmos-sdk reviews...

I'I will copy into tendermint as another PR though. I was not sure which would merge first, tendermint or cosmos-sdk.... Looks like tendermint wins... Bucky the master reviewer :)