Audiotoolbox

- Improved documentation
- renamed writefile method to write_file
- renamed wav submodule to file_io
- moved rms into stats submodule

- Renaming the library to audiotoolbox
- Started refracturing structure for auditory scales
- Implemented a crossfade function
- Added a convolve method to the Signal class
- Added the option to define the first and last sample to be read from file
- Added info function to extract information about an audio file without having to read it

- Reading and Writing Audiofiles is now handled using the soundfile library
- Fixed some tests and depricated numpy apis

- Changed functions in stats to property
- Implemented functions for A and C frequency weighting
- Implemented an add_gain method to the signal class

- Changed a type hint for better backward compatibility

- Added option to generate partly correlated noise with different spectral shapes