Update website links on README.md (#589) [ci skip]
Update website links on README.md (#589) [ci skip]

* Update website links on README.md

Changed the blog links to Medium.
Updated Tendermint website links.

* correct link for Tendermint blog [ci skip]

tendermint/tendermint,tendermint/tendermint,tendermint/tendermint,tendermint/tendermint