Arange improvements

[vkhodygo]

• Current class structure is suitable for testing, but having a function that is package-private feels wrong as it has no checks: all of them are done earlier;
• Use some sort of isclose instead of generic == for comparison of doubles;
• add checks for sets of parameters that have different ranges (potential overflow/underflow):
  • small step and (large) interval might lead to overflow;
  • small interval and (large) step might lead to underflow;
  • small interval and and small step might lead to NaN.