Java-Matrix 2.0 (2016-04-09)

• Version 2.0 released
• Implemented toString, hashCode and equals in Matrix
• Removed Cloneable, replaced by constructor Matrix(Matrix)
• arrayTimesEquals, arrayLeftDivideEquals, minusEquals, plusEquals,
  timesEquals are now void functions, to indicate that they work in-place
  and to make signature more obvious.
• inverse() will now return null if no inverse can be computed, this is
  easier to check since you don't know that in advance and you can easily
  check for being null. It will trigger a NullPointerException anyway if
  you try to dereference it.