cachecontext comments and changelog update

CHANGELOG.md

@@ -7,6 +7,10 @@ BREAKING CHANGES
 * Remove go-wire, use go-amino
 * [store] Add `SubspaceIterator` and `ReverseSubspaceIterator` to `KVStore` interface
 
+FEATURES:
+
+* Add CacheContext
+
 ## 0.14.1 (April 9, 2018)
 
 BUG FIXES

types/context.go

@@ -22,7 +22,6 @@ next decorator or handler. For example,
  	...
  }
 */
-
 type Context struct {
 	context.Context
 	pst *thePast
@@ -172,9 +171,11 @@ func (c Context) WithTxBytes(txBytes []byte) Context {
 	return c.withValue(contextKeyTxBytes, txBytes)
 }
 
-func (c Context) CacheContext() (Context, func()) {
+// Cache the multistore and return a new cached context. The cached context is
+// written to the context when writeCache is called.
+func (c Context) CacheContext() (cc Context, writeCache func()) {
 	cms := c.multiStore().CacheMultiStore()
-	cc := c.WithMultiStore(cms)
+	cc = c.WithMultiStore(cms)
 	return cc, cms.Write
 }