Alexis:

* merkle - proof (non-existence - maybe range)
* intro to light-client and proofs
light-client proofs:
* make this sensible -> very tied to merkle proofs and API
* support new proof types

* expose more proof types in basecoin.Query


* merkle - api cleanup (also Bonsai)
* later: C bindings (to Bonsai?)


* crypto-ledger (while ethan gone)

light-client provider:
* caching checkpoint on Verify
* cleanup (trim old node)