Pybettor

* added functionality to pass various methods to account for margin of bookmaker

* added expected_value_calc() calculates the expected value of given odds based on implied probability

* Added unit tests for all functions
* Reduced complexity of convert_odds()

* Functions added
* bet_prob() calculates probability of bet
* break_even() calculates win rate needed to break even
* fair_odds() calculates fair odds of bet

* Functions changed
* bet_calc() added type castings to ensure correct output and changed output from list to float
* convert_odds() added type casting and changed output from float or dataframe to list or dictionary
* implied_odds() added type casting and changed output from list or dataframe to list or dictionary
* implied_prob() added type casting
* kelly_bet() added type casting and changed output from list to int
* kelly() added type casting and changed output from list to int
* over_round() added type casting and correct documentation for return type
* parlay_calc() added type casting
* true_implied_prob() added type casting and changed output from dataframe to dictionary
* true_probability() added type casting

Functions added
* bet_calc() calculated bet payout
* kelly_bet() calculates dollar amount to bet via Kelly Criterion
* kelly() calculates % of bankroll to bet via Kelly Criterion
* over_round() calculates over round of bet
* parlay_calc() calculates payout of parlay bets
* true_implied_prob() calculates true implied probability
* true_probability() calculates true probability

Functions added
* convert_odds() converts odds to different types
* implied odds() calculates the fair odds from probability
* implied prob() calculates the implied probability from odds