Update bob/beat-devel and sync with available py36/37 builds

This MR updates conda_build_config.yaml to keep both py36 and the new py37 base environments in sync:

• Update versions of bob/beat-devel to 2019.07.31
• Update the version of madmom to 0.16.1
• Add mido-1.2.9 (madmom dependence)