Release 0.2.7

Release 0.2.7 is an addition but will count as a patch release since it is here to fix some issues for the coupling server.

• Added:
  • There is now an option, coupling_pairing, for the BPM pairing in coupling calculation, to let the user choose the number of BPMs instead of the usual "best candidate" method.

What's Changed

• add coupling pairing option by @awegsche and @fsoubelet in #371

Full Changelog: 0.2.6...0.2.7