v0.9.0

Checkpointing v0.9.0

Diff since v0.8.3

Merged pull requests:

• Cleaning up redefinitions in tests (#34) (@michel2323)
• set_zero: Deal with nonnumeric types (#35) (@michel2323)
• Fix reset! export and bump HDF5 deps (#36) (@michel2323)
• Fix EnzymeRules (#37) (@michel2323)
• Fix multilevel and primal (#39) (@michel2323)
• Adding options for writing out checkpoints (#40) (@michel2323)