v0.6.0: upgrades crystal to 1.6.0

What's Changed

• (breaking change) bump crystal support to 1.6.0 by @vrsandeep in #1, #2 and #3

Note that this release will make it incompatible for crystal versions before 1.6.0, due to a breaking change introduced in crystal lang.

Full Changelog: v0.5.0...v0.6.0