New Features

New estimators (frites.estimator.CorrEstimator, frites.estimator.DcorrEstimator) for continuous / continuous relationships (73ed8bb, bc370a9, cf7a345)
frites.conn.conn_dfc supports passing other estimators (a864a7b)
frites.utils.time_to_sample and frites.utils.get_closest_sample conversion functions (7c44478)
frites.conn.conn_ravel_directed reshaping function (f9b9d27)
new frites.workflow.WfMi.copy for internal workflow copy (0c2228c, 860f3d4)
new frites.workflow.WfMiCombine and example class for combining workflows (62072ee)
new classfrites.estimator.ResamplingEstimator trial-resampling estimator (13f6271)

Bug fixes

Fix frites.workflow.WfMi.get_params when returning a single output (3bde82e)
Improve attributes conversion for saving netcdf files (bool and dict) (8e7dddb, c6f7a4d)
Fix Numpy np.float and np.int warnings related (896a198, 7f2a1ca, 0d1a122)