0.15.0

What's Changed

• tidy up lib.rs by @brettmc in #73
• improve exec data access by @brettmc in #74
• improve psr18 exception and retval handling by @brettmc in #75
• String to slice by @brettmc in #76
• Jit server init by @brettmc in #77
• prepare for 0.15.0 by @brettmc in #78

Full Changelog: 0.14.0...0.15.0