Don't use the matplotlib printer if matplotlib raises an exception

Fixes #2822.
Use \left [/(/{ \right ]/)/} for latex of lists, tuples and dicts

This makes them still work with the matplotlib.mathtext renderer, which
doesn't support matrices.
Fix latex doctests
Classification of nonlinear sysode for 1st order 3 eq

This commit has the method to classify nonlinear system of 3 ODEs of first order. It contain six type of equation which considered here.
method for 3 type of 3 nonlinear sysode of 1st order

This contains definition of sysode_nonlinear_3eq_order1 and definition for solving three types of 3 nonlinear system of ODEs of first order.
nonlinear sysode 3eq order1 type4
Add tests to test_wester.py for set theory and continued fractions.

Also for symbolic continued fractions.
Added type5 and few test cases