docs: add info about tm-migrate

docs/ecosystem.rst

@@ -115,3 +115,8 @@ Deployment Tools
 See `deploy testnets <./deploy-testnets.html>`__ for information about all the tools built by Tendermint. We have Kubernetes, Ansible, and Terraform integrations.
 
 Cloudsoft built `brooklyn-tendermint <https://github.com/cloudsoft/brooklyn-tendermint>`__ for deploying a tendermint testnet in docker continers. It uses Clocker for Apache Brooklyn.
+
+Dev Tools
+---------
+
+For upgrading from older to newer versions of tendermint and to migrate your chain data, see `tm-migrator <https://github.com/hxzqlh/tm-tools>`__ written by @hxzqlh.

docs/using-tendermint.rst

@@ -386,3 +386,11 @@ the listening addresses of the various sockets don't conflict.
 Additionally, you must set ``addrbook_strict=false`` in the
 ``config.toml``, otherwise Tendermint's p2p library will deny making
 connections to peers with the same IP address.
+
+Ugrading
+~~~~~~~~
+
+The tendermint development cycle includes a lot of breaking changes. Upgrading from
+an old version to a new version usually means throwing away the chain data. Try out
+the `tm-migrate <https://github.com/hxzqlh/tm-tools>`__ tool written by @hxqlh if
+you are keen to preserve the state of your chain when upgrading to newer versions.