[Find peacks C extension] Add a Python fallback to provide a pure Python scared version

Summary

Due to the C extension used for find peaks signal processing function, the installation of scared needs:

• to work on a platform for which a binary is available (pretty limited)
• to have a C compiler installed, which is not so easy to solve on all environments if you are not a a developper

It would be desirable to be able to distribute a pure Python wheel binary distribution of scared, by using a pure python fallback of find peaks.

To do that, we should provide:

• a source distribution where find peaks is compiled if possible, otherwise use pure python fallback.
• a binary universal distribution where the fallback is used
• platform specific libraries with compiled find peaks included (available)