Added a 'separation' behavior; some mild tidying.
Replaced the 'accelerative' parameter; useful if you don't want the behavior to alter your speed.
Flee example should be accelerative.
Standardize parameters and comments for clarity.
Was incorrectly clamping vector dot product to -1..1 -- fixed.
Can now compute closest approach time, positions, and distance for two kinematics.
Both 'pure' and 'clamped' dot products are supported.

Clamped is for when you know you'll use acos() on the result and can't afford a result outside -1.0..1.0 that might creep in due to rounding errors and whatnot.
Use clamped_dot where appropriate.
Output useful for debugging but commented out.
Some nice constants for certain key vectors.
Can now pass arrival radius to 'arrive'; arrival is determined by VEC_ZERO force.
Commentary/doc.
A "canonical", predictive collision-avoidance / separation behavior.
Tidying and commentary.
The separation example now has multiple threats moving around to avoid.
Readme, gemspec, changelog for new version.