- Option to initialise the class with non keyword arguments (eg. `UnitConvert('bytes', 100, 'kilobytes', 100)`).
- Access converted values via `__getitem__` (eg. `UnitConvert(mb=512)['gb']`).
- To give a more dict-like approach, available conversions can be accessed via `keys`, with support for `get`, `values` and `items`.
- Added temperature conversions.
- Added deprecation warning.