ENH - Replace ``sklearn`` by ``celer``

[Badr-MOUFAD]

This aims to use celer solver instead of sklearn.

• [x] documentation (building plots)
• [x] unit test

closes #135

[mathurinm]

Thanks Badr

@Klopfe @QB3 was there a particular reason for which we used sklearn's Lasso instead of celer's ?

[Klopfe]

Thanks Badr

@Klopfe @QB3 was there a particular reason for which we used sklearn's Lasso instead of celer's ?

hmm... Not that I know of...

[mathurinm]

small failure here : https://github.com/QB3/sparse-ho/runs/6920007820?check_suite_focus=true#step:5:184 celer Logisticregression does not support multiclass so you need to keep sklearn's

I would use sklearn LogisticRegression everywhere in fact because it is quite fast (relying on liblinear etc)