PyAT 0.2.1

What's Changed

• first look at PolynomB in *LinearPass by @swhite2401 in #290
• Test for use of keep_lattice in find_orbit6(). by @willrogers in #301
• Avoid W and Chrom calculations in transfer line mode by @swhite2401 in #304

Full Changelog: pyat-0.2.0...pyat-0.2.1