Big-num-format

- Bug: Fix string index error appearing sometimes ([issue 8](https://github.com/MBmasher/big-num-format/issues/8))
- Bug: Only strip trailing zeroes and not leading zeroes when formatting numbers.
- Bug: Fix bug with magnitude showing incorrect values ([issue 12](https://github.com/MBmasher/big-num-format/issues/12))
- Enhancement: Allow format_num() to be able to take strings, and convert the input into a Decimal class ([issue 10](https://github.com/MBmasher/big-num-format/issues/10))
- Minor: Remove redundant function get_magnitude() ([issue 11](https://github.com/MBmasher/big-num-format/issues/11))
- Minor: Remove leading whitespace when only one number is returned

- Bug: Fix characters showing up before number names ([issue 3](https://github.com/MBmasher/big-num-format/issues/3))
- Bug: Fix decimal points randomly showing up ([issue 4](https://github.com/MBmasher/big-num-format/issues/4))
- Enhancement: Implement rounding in format_num() ([issue 5](https://github.com/MBmasher/big-num-format/issues/5))
- Enhancement: Add an argument to format_num() which specifies decimal places ([issue 1](https://github.com/MBmasher/big-num-format/issues/1))
- Minor: Small text changes to README.md