Mcplot

- Add `get_color` to get value of named colors known to Matplotlib.
- Added named colors of the guidelines of the Helmholtz Centre for
Environmental Research - UFZ, Leipzig, Germany.

- Added 'order' keyword to `get_cmap`.

- Changed order of color maps in printing and plotting.
- Edited docstrings of color module to follow closer numpydoc.

- Use `text2plot` in `abc2plot` and `signature2plot`.
- Better handling of linebreaks in Matplotlib and LaTeX mode in `str2tex`.
- Added `text2plot`, adding text onto a plot.
- Added `int2roman` and `roman2int`, converting integer to and from
Roman literals.
- Combine `abc2plot` and `signature2plot` in one file `text2plot.py`.
- Added `abc2plot`, adding a, B, iii), etc. onto a plot.
- Added `signature2plot`, adding a copyright notice onto a plot.
- Added 'pyjams_color.pdf' as reference to available colormaps.

- Added tests for `color`.
- Added 'pragma: no cover' to plot and MPI sections of codes so that they
are not included in coverage report.
- Cleaned mcPlot docstrings.
- Added current colors of Paul Tol, i.e. sron color palettes.

- Add `position`, which positions arrays of subplots to be used with
Matplotlib's add_axes.