**What is fixed** Add link to the issue this PR fixes. 

Example: Fixes #42. 

**Why is this change proposed** If this change does *not* fix an open issue, briefly describe the rationale for this PR.

**What is changed** Briefly describe the changes proposed in this pull request: 

* Fixed rare exception happening in `x >= 42` case
* Small optimization of `decompress()` method
* Corrected API doc for `compress()` method to reflect current implementation