rename src to pylib and in data.seq float rounding uses start as well

tests/test_ode.py

@@ -19,7 +19,7 @@ from matplotlib.pyplot import figure, subplots, plot, show
 
 import os
 import sys
-sys.path.insert(0, os.path.abspath('../src'))
+sys.path.insert(0, os.path.abspath('../pylib'))
 from numerical.ode import (e1, e2, e4, i1, newmark_newtonraphson,
   newmark_newtonraphson_rdk)
 from numerical.ode_model import disk, disk_nm, disk_nmmdk