add Google Analytics for documentation pages (#2645)
add Google Analytics for documentation pages (#2645)

We need Google Analytics to start measuring how many developers are viewing our documentation. That way we can gauge how successful an/or useful various pages are. VuePress supports GA and all we have to provide is the tracking code.

This PR also renames the static docs site to "Tendermint Documentation", which is a better representation of the contents than only "Tendermint Core".
tendermint/tendermint,tendermint/tendermint,tendermint/tendermint,tendermint/tendermint