feat(analysis/calculus) : L'Hôpital's rule, 0/0 case (#3740)
This proves several forms of L'Hôpital's rule for computing 0/0 indeterminate forms, based on the proof given here : [Wikibooks](https://en.wikibooks.org/wiki/Calculus/L%27H%C3%B4pital%27s_Rule). See module docstring for more details.
