Ingest files containing collapsed stacks and tolerate invalid lines,
like FlameGraph does.
Some files might contain lines starting with a # to add comments to the
collected samples. Speedscope should still attempt to parse these files
as collapsed stacks and only keep the samples that it can find. Only
fail if there are no samples reported.
Before this PR, we blindly assumed that all text imported into speedscope was UTF-8 encoded. This, unsurprisingly, is not always true. After this PR, we support text that's UTF-16 encoded, with either the little-endian or big-endian byte-order-mark.
Fixed#291
This should help keep things organized as speedscope supports more languages & more formats
Test Plan: Try importing from every single file type, see that the link to load the example profile still works
