collection of minor bugfixes and feature enhancements

Minor bugfixes and minor feature additions that accumulated over the past year:

Bugfixes:

• changed interpolation method to linear instead of cubic to avoid artifacts
• fixed bug in lmsal downloader
• fixed bug in wcs coordinate conversion (offset by 1 pixel)

Under the hood:

• made coordinate representation and conversion entirely dependent on astropy's WCS

Features:

• added a function to extract features from Magnesium II h/k profiles
• added retry loop for failed hek requests

minor bugfixes

A few minor bugfixes to conform to the rules of pypi

first release

This is a first release of IRISreader in order to commit it to PyPI.
IRISreader is at this point still not very well documented in all its depth, feel free to send questions, suggestions and feedback to cedric.huwyler@fhnw.ch.