Official release of rgfrosh corresponding to the reviewed JOSS version with updated tests.

Add missing attrs dependency

Warning
Breaking changes from v0.1.4

• Implemented base Shock class
• Added IdealShock class
• Fixed bug in FrozenShock solver for initial conditions from target conditions
• Changed FrozenShock.__init__ function signature and replaced target_conditions classmethod

Full Changelog: v0.1.4...v0.2.0

Change log:

• Converted module to package with constants, shock, and interface submodules
• Added CoolProp interface (rgfrosh.interface.CPInterface)
• Renamed relative_tolerance to rtol
• Add unit testing

Added functionality for calculating initial conditions for target post-reflected-shock conditions. Improved documentation.