Update to tendermint 0.34.2

As we are building the lazyledger app using the latest version of the SDK (https://github.com/lazyledger/cosmos-sdk/pull/11), we should update ll-core to use the equivalent of [0.34.1](https://github.com/tendermint/tendermint/releases/tag/v0.34.1) of tendermint.

ref: https://github.com/lazyledger/cosmos-sdk/issues/2