Fix end integration with more than 1 singularity.
Fix end integration with more than 1 singularity.

Replace np.allclose with np.isclose. np.allcose will return true / false
by comparing two whole arrays. np.isclose returns True/False for each
element. Need to endpoints of intervals to singularities array.

jensv/fluxtubestability,jensv/fluxtubestability