Adds cmake as a build dependency

[fakufaku]

The PR adds cmake as a build dependency.

Problem

On some systems (e.g., google colab), the cmake python package is pre-installed.
In this case, the cmake command calls a script that calls this package instead of the original cmake executable.

However, the python build system will create an empty build environment where the cmake python package is not available, leading to an import error.

See issue #15

Solution

Adding cmake as a build dependency solves the problem by installing the cmake python package as part of the build environment.

[tuxu]

Lgtm!