Remove float comparisons where Fraction comparisons would be better

Fixes https://github.com/0xfe/vexflow/issues/234 -- multiple non-power-of-two ticks added together sometimes cause floating point comparison problems. Replaces all comparisons of FractionA.value() == FractionB.value() with FractionA.equals(FractionB) and adds Fraction.lessThan, Fraction.greaterThan, etc.