go.tools/README: minor correction.
go.tools/README: minor correction.

R=gri
CC=golang-dev
https://codereview.appspot.com/18490043

d0f/go-zh.tools,webfd/go-zh.tools,skyportsystems/go.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,skyportsystems/go.tools,d0f/go-zh.tools,skyportsystems/go.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,8limbs/gotools,d0f/go-zh.tools,d0f/go-zh.tools,8limbs/gotools,bryanxu/go-zh.tools,d0f/go-zh.tools,webfd/go-zh.tools,skyportsystems/go.tools,webfd/go-zh.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,8limbs/gotools,skyportsystems/go.tools