GSoC Week 11-13

I am reaching the final stages of my project well ahead of the schedule.

Both the Crosspectrum and Powerspectrum classes, the Lomb Scargle Fourier Transform and Basic Documentation have been completed. Tests are almost done too

I have double checked with Matteo that the results are consistent using multiple examples and they are close to expected results.

The following are the documentation notebooks on how to use the classes.