Assignment 1

Implementation of Assignment 1 (#9)

- Gaussian solver initial implementation
- Add some unit tests
- Matrix methods are no longer static methods in a class.
- Refactor to support automation
    - Added exiting with exit codes to support automation
    - Moved application code into src directory
    - Made application code runnable from parent directory using `python -m
        src`.
- Moved make and solve into their own modules. This will hopefully make it
    easier to address changes to those specific units in the future.
- Added --directory option for make action
- Changed default export location for matrix definition files to
    `/tmp/makemat`.
- Added github actions
- Added code formatting with black

Resolves #3
Resolves #4
Resolves #6
Resolves #7