Puncturedfem

* Added **ex1b-pacman.ipynb**
* Added **ex1c-ghost.ipynb**
* Updated **ex1a-square-hole.ipynb** with more accurate reference values

* Added `compute_h1()` and `compute_l2()` methods to `locfun`
* Added `integrate_over_cell()` method to `polynomial`
* Added methods to `contour` and `cell` to integrate over the boundary without multiplying by the norm of the derivative (i.e. 'preweighted' integrands)
* Monomials now default to zero monomial
* Fixed evaluation of zero `monomial` and zero `polynomial` to return same size as input
* Removed `ext_pt` field from `cell`
* Added `id` field to `contour`
* Added `get_integrator()` method to `contour` (`cell` inherits)
* Added `neumann` module to `nystrom` for solving Neumann problem
* Modified `harmconj` module accordingly
* Completely overhauled anti-Laplacian calculation for punctured cells
* **ex1**: "Square with circular hole" updated

* Added **/poly** subpackage
* `monomial` and `polynomial` objects
* Added **locfun/** subpackage
* `locfun` object holds all data for local function $v\in V_p(K)$
* Added `ext_pt` field to `cell` object, which is an exterior point such that centering the origin at `ext_pt` placing the cell strictly in the first quadrant

* MATLAB code rewritten in Python to increase accessibility
* Examples presented with Jupyter Notebook
- **ex0-mesh-building**:
defining edges, cells, and meshes
- **ex1-inner-prod**:
compute $H^1$ and $L^2$ (semi-)inner products on punctured cell
* New subpackages/modules
- **quad**: trapezoid, Kress, and Martensen quadrature objects
- **mesh**: mesh construction tools
- **edge**: parameterization of an edge
- **contour**: collection of edges forming a simple closed contour
- **cell**: mesh cell (subclass of contour)
- **plot**: functions for
- plot edges, contours, cell boundaries
- trace of a function along a collection of edges
- **nystrom**: Nystr$\text{\"o}$m method for solving integral equations
- includes single and double layer operators
- block system support
- **d2n**: Dirichlet-to-Neumann map for harmonic functions
- computation of harmonic conjugate
- FFT (anti-)derivatives
- **antilap**: tools to compute anti-Laplacians of harmonic functions
* Added unit tests to **puncturedfem/test/**
- **test_harmconj** for harmonic conjugates
- **test_fft_deriv** for FFT differentiation

Only a simple diffusion operator (the Laplacian) is currently supported.
Dirichlet and mixed Dirichlet-Neumann boundary conditions are available,
but are assumed to be homogeneous. Used to run a simple "pegboard" example.