v0.3.7

Added

• tetragono: Add support to calculate deviation of the observer set as a whole, which is useful since many observables
  are the summation of several local observables.
• tetragono: Add arguments support for gm_conf_create and ap_conf_create in tetragono shell.
• tetragono: Add a member dict called attribute to AbstractState, which may contain customed data used by user.

Changed

• tetragono: save_result accept another parameter, which is the total result of the whole observers set. Its
  signature is state, result, whole_result and step now.
• tetraku: Change the defnition of x/y/z link in kitaev model. The bond inside one tensor is z link now.
• tetragono: gm_run(_g) will now return/yield all the measurement result instead of energy only.

Deprecated

• tetragono: The previous signature of save_result: state, result and step is deprecated.

Removed

• tetragono: Remove the deprecated function natural_gradient and the deprecated paramter metric_inverse_epsilon
  for gm_run.