Changes in version 0.99.0 (2019-06-02)
+ Initial submission

Changes in version 1.1
+ Only convert 0's to NA's if there are no NA's in the dataset (commit 06df44a, fix issue #3)

Changes in version 1.3
+ Escape result coefficient names if result_names() is called and they contain potentially 
problematic characters (see issue #4)

Changes in version 1.11
+ Fix copy and paste bug that meant that the wrong value was used in the unregularized 
feature estimation procedure (see #18. Thanks to @amackey for spotting the bug).

Changes in version 1.17
+ Check that sigma2 is larger than zero (see #21. Thanks to @elena-krismer)