Move tests and demos out of psignifit package

[pberkes]

Fix #128

[lschwetlick]

@guillermoaguilar I guess we will need to make sure to adjust the docs accordingly, because we are compiling those demos into the docs.

[otizonaizit]

@guillermoaguilar I guess we will need to make sure to adjust the docs accordingly, because we are compiling those demos into the docs.

well, as far as I understood from the discussion in #181 , those notebooks are jut waiting to be migrated into the new documentation created with jupyter-book, so they will be gone soon anyway. Otherwise the PR looks good to me!

[guillermoaguilar]

well, as far as I understood from the discussion in #181 , those notebooks are jut waiting to be migrated into the new documentation created with jupyter-book, so they will be gone soon anyway. Otherwise the PR looks good to me!

YES!

[pberkes]

I had to juggle a little because github was stopping me from merging, reporting a merge conflict that was not present when merging on the command line... anyway, now I merged manually and it looks alright