p-winds v1.4.4

Version 1.4.4 of p-winds calculates the density profiles of exospheric metals! Here is the changelog:

• New module: carbon.py is used to calculate the distribution of neutral, singly-ionized and doubly-ionized carbon in an exoplanet's upper atmosphere.
• New module: oxygen.py is used to calculate the distribution of neutral and singly-ionized oxygen in an exoplanet's upper atmosphere.
• New module: lines.py stores spectral line information. This information was previously stored in microphysics.py, but was moved to avoid bloating the latter module. Please pay attention to this new usage of microphysics.py! As always, check the documentation to learn more.
• helium.py now includes a function ion_fraction() that calculates the ion fraction of helium more quickly than the population_fraction() function.
• The function make_spectrum_from_file() now has an option to scale an input spectrum by systemic distance and the semi-major axis of a planet around it.
• New examples in the documentation: Roche lobe effects and exospheric metals.
• General bug fixes and updates to docstrings.

A paper describing the carbon and oxygen modules is being submitted for refereed publication soon. As always, please check the documentation of the code for guidance on the functions parameters!