Read the entire STDIN.

The problem with reading synchronously from /dev/stdin is that you can get a
spurious EOF when the input buffer is empty, even if more content is coming. Now
STDIN is read from a loop, and only stops polling when all input has been read.
This fixes #70 #85 and other errors related to parsing large files on STDIN.
Merge pull request #146 from mbostock/read-all-stdin

Read the entire STDIN.