v1.4.0

Custom Functions

• Define custom functions and redefine built-in functions when parsing
  an expression. See docs and example.
• Use MathNodeExpression.getPotentialFunctionNames() to detect potentially
  used functions in a string.
• Use period in the middle of custom variable and function names.
• Under-hood, functions now support multiple comma separated arguments, so
  you can supply multiple arguments to your custom function.
• Detect custom functions im math tree using
  MathExpression.getUsedFreeformFunctions().

Breaking changes

• MissingFunctionArgumentListException renamed to
  OutOfRangeFunctionArgumentListException
• MathNodeExpression.fromString() may throw other errors besides
  MathException
• MathNodeExpression.getPotentialVariableNames() is replaced by
  MathNodeExpression.getPotentialDefinable()
• Instead of log[base](arg), you should pass log(base, arg) syntax now
• Period is an allowed character in the middle of a variable name now

Misc.

• UnexpectedClosingBracketException and BracketsNotClosedException can
  now tell where the problem probably happened.
• New MathParseException's InvalidFunctionNameException,
  DuplicateDeclarationException, InvalidFunctionArgumentsDeclaration.