Reorganize repo

[raimis]

This is preparation for a conda-forge package.

• Reorganize the files
• Improve the build system
  • Build the library
  • Build the test executables
  • Run the tests
• Update the documentation

[raimis]

The minimal reorganisation towards a conda-forge package is done.

@mikemhenry could you check if something more is need for a feedstock?

@peastman could you review the rest?

[mikemhenry]

This looks good! It shouldn't be too hard to package since all the dependencies are on conda-forge.

[raimis]

@peastman can we merge this?

[peastman]

Looks good. Thanks!