Added the EulerCromer method fully implemented as an example of
subclassing.
Added UnitConverter
Changed Random class to be a pure static Random class. This should
probably be implemented with a Singelton design pattern instead: http://
Added mass and resetVelocityMaxwellian on Atom.
Removed reset forces in VelocityVerlet.
Fixed so IO can have an open movie file so xyz-movies can be created.
Wrote a comment or something in statisticssampler.cpp.
Added a couple of functions in System.
Added ostream operator to vec3 for easy output with cout.
Created example program with one atom.