add some clarification to module.exports in README
add some clarification to module.exports in README

If flow is created in the same file that you use
the flow then the export is not needed. However if
it will be created in a separate file from the file
you run, then it needs to be exported with
`module.exports`

sgml/bench-rest,nishant8BITS/bench-rest,kyroskoh/bench-rest,jeffbski/bench-rest