ri: Fix colon handling in class completion.

completions/ri

@@ -35,7 +35,7 @@ _ri_get_methods()
 _ri()
 {
     local cur prev words cword
-    _init_completion || return
+    _init_completion -n : || return
 
     local class method prefix ri_path ri_version separator IFS
     local -a classes
@@ -75,6 +75,8 @@ _ri()
     fi
 
     COMPREPLY=( $( compgen -W '${classes[@]}' -- "$cur" ) )
+    __ltrim_colon_completions "$cur"
+
     if [[ "$cur" == [A-Z]* ]]; then
         # we're completing on class or module alone
         return 0