Clarify what should be committed in README

I understand the [docs need lots of work](tools#122 (comment)) but I think this line should be updated soon to include the decision made in tools#123, even if a big rewrite is coming.  It has [confused me](tools#131 (comment)) and [several other people](http://stackoverflow.com/questions/26334220/should-i-commit-godeps-workspace-or-is-godeps-json-enough/26342342#26342342).

Readme.md

@@ -24,7 +24,7 @@ it's one command to start using:
 This will save a list of dependencies to the file Godeps/Godeps.json,
 and copy their source code into Godeps/_workspace.
 Read over its contents and make sure it looks reasonable.
-Then commit the file to version control.
+Then commit the whole Godeps directory to version control, [including _workspace](https://github.com/tools/godep/pull/123).
 
 #### Restore