This improves performance on the test.yaml attached to #158 by about
25% on my machine as compared to the previous commit (0.25s -> 0.20s),
as measured by `time build/util/parse < test.yaml > /dev/null`.
This improves performance on the test.yaml attached to #158 by about
35% on my machine (0.39s -> 0.25s), as measured by
`time build/util/parse < test.yaml > /dev/null`.
On my Macbook Pro, reading from standard input incurs a bunch of locking
overhead, which complicates profiling and (IMO) adds noise to
results. This adds the option to read from a file, which doesn't incur
this overhead.