Miscellaneous fixes to the CSS stylesheet

There were a couple things that needed to be changed in this file:
    - There was a mixture of tabs and spaces, I've changed it to be all
      spaces.
    - There were no credits at the top of this file.
    - I've added style for the tabs that were not allowing any scrolling
      when the contents exceeded the vertical space available, concretly
      fixing #235.
Add extra padding to some of the divs

The padding had to be added in the form of <br> tags because there's
a problem with the jQuery ui-tabs not scrolling properly.
Add @antgonza to the credits in emperor.css
Merge pull request #237 from ElDeveloper/issue_235

Fixes scrolling not working in some of the UI tabs
Change minimum treshold and tests for % explained
Fix formatting to use two decimal places

Changing the minimum threshold for an axis to be considered, required us
to change the formatting of the string to have two decimal places,
otherwise it would show 0 for values < to 1.

Fixes #226
Fix error as pointed out by @antgonza
Merge pull request #240 from ElDeveloper/issue-226

Fixes issue 226 - minimum percent explained
Category names are no longer trimmed

Fixes category names being trimmed at more than twenty five characters,
now the names are just displayed on screen.

Fixes #94
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 message in the ChangeLog.md file

Add message describing that the category names are no longer trimmed to
24 characters.
Fixes key tab not using the available space

The key tab was not previously using all of the available space on
screen, I've made some changes to the CSS sheet to make this the case
and added some padding when the table is formatted.

Fixes #158
Add note to changelog about the key tab
Merge pull request #243 from ElDeveloper/issue-158

Fixes key tab not using the available space
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
Merge branch 'master' of git://github.com/qiime/emperor into issue-94

Conflicts:
	ChangeLog.md
Merge pull request #241 from ElDeveloper/issue-94

Category names are no longer trimmed
Merge branch 'master' of git://github.com/qiime/emperor into issue_150

Conflicts:
	ChangeLog.md