v2.12.1

ComplexMixtures v2.12.1

Diff since v2.12.0

• print further information on trajectory initial opening and reading frames

Merged pull requests:

• print opening trajectory message (#80) (@lmiq)
• implement show determination of number of frames in NamdDCD (#81) (@lmiq)
• set version to 2.12.1 (#82) (@lmiq)