Goosempl

* Added power law annotations (`plot_powerlaw`, `text_powerlaw`, and `grid_powerlaw`).
* Added function to convert to and from relative coordinates.

Added two functions to annotate in a (semi-)log plot or to annotate a powerlaw. The trick is that you can specify coordinates in 'relative' coordinates. Checkout:

* `rel2abs_x`
* `rel2abs_y`
* `plot_powerlaw`
* `text`

* Added `hist` to plot a histogram.
* Added different histogram binning: `histogram_uniform` and `histogram_log`.
* Simplified `cdf` (plotting must now be separate).

The style definition now adapts to the system. To this end, it's entire definition is moved the the Python module goosempl.

The style definition now adapts to the system. To this end, it's entire definition is moved the the Python module goosempl.

Updated installation to be more robust.