Proposal: Add lite client routes

[cwgoes]

Most applications built on the SDK (and certainly a nameservice) will want lite client RPC functionality, I think we should demonstrate a minimum viable example of what that looks like.

Might block on cosmos/cosmos-sdk#1081.

[alexanderbez]

Yes!!!

[jackzampolin]

Definitely! This is blocked on cosmos/cosmos-sdk#1081

[jackzampolin]

So this is no longer blocked, and I've done about 1/2 the work here (the code side). We still need a series of HTTP calls to show users how to call the routes (maybe in a tutorial/run-rest.md).