Skeleton documentation for the package
Skeleton documentation for the datasets
Skeleton code for the mex class and main command

Defines the `mex` S3 class, with a minimal set of constructors and methods.
This includes defining `mex()` as a generic function, which will be the main
command that users will run.
Merge pull request #6 from tierneyn/main-method

Damjan's S3 Class changes