Method Acting (v1.2.1)

This totally didnt take a few hours to work on, and not at all because I am too indecisive. wdym?

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Features:

• Created methods for users to set values for stiffness, damping, and mass, and allow chaining for it (9b2b338)

Changes:

• Set values in :new() instead of using methods, and included it in the meta table initialization (9b2b338)

Full Changelog: v1.2.0...v1.2.1