Fix Mean

[rymo4]

• Makes the mean actually report the mean (fixes #1)
• Adds a test for the mean
• Bumps the version
• Pulls apart some of the stat processing into new methods for easier testing

[rymo4]

@jehiah Can you take a look at this? I also have another pull request open on this repo that has been sitting around for a while. Thanks in advance.

[rymo4]

@jehiah rebased/squashed