Prepare a new compatibility release v0.6.6. (#203)

Revert the breaking API and package structure changes on master, and
prepare to tag a new release compatible with the previous v0.6.4 so that
normal upgrades with go get will function correctly.

The API changes in tag v0.6.5 have been preserved in the new package-reorg
branch, so that any existing dependents will continue  to work. 

Other changes since v0.6.4, including config file changes and CI updates, are 
maintained on the trunk. This also folds in the merge commit from  #187.

Co-authored-by: Dev Ojha <ValarDragon@users.noreply.github.com>

.gitignore

@@ -11,4 +11,5 @@
 # Output of the go coverage tool, specifically when used with LiteIDE
 *.out
 
-.idea
+.idea
+vendor/*

CHANGELOG.md

@@ -1,18 +1,28 @@
 # Changelog
 
-## 0.6.5
+## 0.6.6
 
-**2021-08-04**
+**2021-11-08**
+
+**Important note:** Version v0.6.5 was accidentally tagged and should be
+avoided.  This version is identical to v0.6.4 in package structure and API, but
+has updated the version marker so that normal `go get` upgrades will not
+require modifying existing use of v0.6.4.
 
-### Breaking changes (Go API)
+### Version bumps (since v0.6.4)
 
-- [metadb] [\#151](https://github.com/tendermint/tm-db/pull/151) split backends into packages and add metadb (@marbar3778, @mvdan)
+- Bump grpc from to 1.42.0.
+- Bump dgraph/badger to v2 2.2007.3.
+- Bump go.etcd.io/bbolt to 1.3.6.
 
-### Version bumps
+## 0.6.5
+
+**2021-08-04**
 
-- Bump dgraph/badger to v2.
-- Bump go.etcd.io/bbolt from 1.3.5 to 1.3.6.
-- Bump grpc from 1.35.0 to 1.38.0.
+**Important note**: This version was tagged by accident, and should not be
+used. The tag now points to the [package-reorg
+branch](https://github.com/tendermint/tm-db/tree/package-reorg) so that
+any existing dependencies should not break.
 
 ## 0.6.4