2.0.1: minor bug fixes

This release sees two minor bug fixes:

• skued.diffshow will temporarily switch PyQtGraph's image axis order to the row-major, which is a saner default.
• Fixed an issue where a typo in electron_velocity would raise an exception.

There is also a new way to quickly look at images:

• Added skued command-line utilities. Images can be shown (with interactive viewer) using skued diffshow [path].
  Crystal information can be determined using skued crystinfo [path].