Updating the docs to note the caching.

README.md

diff --git a/README.md b/README.md
index 5d97527..2d93340 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,7 @@
     - hg
     - svn
 * Support custom local and global plugins (see docs/plugins.md)
+* Repository caching including reuse of packages in the `$GOPATH`
 
 ## How It Works