v0.6.0

Major bug fix release

• Fixes building on 32 bit machines (thx @cgmb)
• Sets error messages on failures according to Argon2 implementation
• General fixes to options parsing
• Allows to install outside git repositories
• Benchmarks added (not available from npm)

This is probably the last unstable version before final 1.0.0, and I will test it on production for a while before releasing it stable.