[WIP] Created reciprocal class and added tests

Put sech and csch in a ReciprocalHyperbolicFunction class and added some
tests for their basic functions.
Will add more tests after resolving test errors.
[WIP] Added some tests and created Reciprocal class

Created a ReciprocalHyperbolicFunction class to avoid code duplicity.
Also corrected the error in the trigonometric csc function so that tests
pass.