QTR

Implemented quasi time reversible, improved options. Added a test for the quasi time reversible.

tests/test_extrapolation.py

@@ -9,7 +9,7 @@ import gext.grassmann
 import utils
 
 SMALL = 1e-10
-THRESHOLD = 2e-2
+THRESHOLD = 5e-2
 
 @pytest.mark.parametrize("datafile", ["urea.json", "glucose.json"])
 @pytest.mark.parametrize("fitting", ["leastsquare", "qtr"])