text: Title: Modify to be more pythonic
  Body: - [x] Remove `type` parameter for `def make_translate_slider` It is not used and it doesn't make any sense.
   https://github.com/mithi/hexapod-robot-simulator/blob/5c1f8a187e7497a37e9b2b5d66ec2fe72b3cc61f/widgets/ik_ui.py#L34
  
  - [x] Use None instead of {} as default parameter as per convention
  https://github.com/mithi/hexapod-robot-simulator/blob/5c1f8a187e7497a37e9b2b5d66ec2fe72b3cc61f/widgets/pose_control/kinematics_section_maker.py#L28
    - dangerous-default-value (W0102) Dangerous default value %s as argument Used when a mutable value as list or dictionary is detected in a default value for an argument.
    - See also  https://stackoverflow.com/questions/26320899/why-is-the-empty-dictionary-a-dangerous-default-value-in-python/26320917
  
  - [x] It seems like we don't actually need to store n_axis as an attribute
  https://github.com/mithi/hexapod-robot-simulator/blob/5c1f8a187e7497a37e9b2b5d66ec2fe72b3cc61f/hexapod/models.py#L108