Add a few missing features to the changelog

For some of the branches that have been merged lately, these have gone
in to the master branch without being mentioned in the ChangeLog.md
file.
Add note about the mantissa
Merge branch 'master' of git://github.com/qiime/emperor into missing-changelog-notes

Conflicts:
	ChangeLog.md
Merge pull request #242 from ElDeveloper/missing-changelog-notes

Add a few missing features to the changelog