v0.5.1

By pulling in the latest ion-rs, this release fixes a bug that caused a NOP pad followed by an IVM to be considered illegal.

What's Changed

• Upgrade ion-rs dependency to v1.0.0-rc2 by @zslayton in #82
• Version bump to v0.5.1 by @zslayton in #83

Full Changelog: v0.5.0...v0.5.1