Fixed bug in tests for poll_fd and file watcher

cc: @loladiro - please verify before merging.

The tests used ```int64(time() * 1000)``` to get time differences in milliseconds.  Since int64 is a rounding function, it could have caused inaccuracies in calculating the same.

Replaced to use tic() and toq() .

Also deleted a redundant line in stream.jl