Xpart version 0.8.5

Changes:

• build_particles accepts nemitt_x and nemitt_y (scale_with_transverse_norm_emitt is deprecated).
• build_particles can match transverse distribution using the 4d twiss (usage: build_particles(..., method="4d", ...).
• Read-only check in Particles.energy.
• Version number accessible as xobjects.__version__.

Full Changelog: v0.8.4...v0.8.5