Xdeps version 0.8.2

Changes:

• Add zero_if_met in MeritFunctionView and use it to stop search with scipy scalar optimizers.
• Disable xatol by default in run_simplex.
• Introduce Optimize.run_direct(...).
• Better messages in Optimize.run_... methods.

Full Changelog: v0.8.1...v0.8.2