Fixed the introduction and equations

Addresses #20
Merge branch 'master' into issue20
Clean up notebook.

 - [x] Fix initial Equations
 - [x] Include image of microstructure discretization
 - [ ] Add in an improve description of the Fourier transform and circulant matrix theorem (not finished)

Address #20
Clean up notebooks to demonstrate redundant coefficients.

`cahnHilliard1.py`:

 - [x] Add in an improve description of the Fourier transform and circulant matrix theorem
 - [x] Add an image of the broken coefficients at the end of cahnHilliard1.py

`filter1D.py`:

 - [x] Demonstrate the redundancy issue.
 - [x] Show the `MKSRegressionModel`
 - [x] Show results with and without the redundancy issue

Address #20
Clean up notebook for issue #20.

`cahnHilliard2.ipynb`:

 - [x] Use `MKSRegressionModel` to show sklearn cross validation
 - [x] Remove `MKSRegressionModel` intro, which is now in
   `filter1D.ipynb`.
Merge branch 'issue20'

Fix #20