Travis: Call pip3 with full path.
Travis: Call pip3 with full path.

msteinbeck/tinyspline,retuxx/tinyspline,msteinbeck/tinyspline,retuxx/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,msteinbeck/tinyspline,retuxx/tinyspline