implement some FS operations for rsign2#429

Merged

bors[bot] merged 3 commits intomasterfrom feature/wasi-fs-ops-for-rsign2

May 10, 2019

+185-35

Commits on May 9, 2019

implement some FS operations for rsign2
Mark McCaskey
committed

Commits on May 10, 2019

major improvements to wasi fs calls; include explanation in unimpl!s
Mark McCaskey
committed
clean up, update changelog
Mark McCaskey
committed