Enhancing TWave

**ToDo**

- [x] Make rewrite methods work
I'm not sure if this is the correct way to represent it. It has to be an equation equating to zero.
```
      2              2         
     ∂              ∂          
ε⋅μ⋅───(E(x, t)) + ───(E(x, t)) = 0
      2              2         
    ∂t             ∂x 
```