Fix typo in `Vsibility` -> `Visibility`
Merge pull request #249 from ElDeveloper/typo

Fix typo in `Vsibility` -> `Visibility`
ENH: Add toggle visible button

The selected categories under the visibility tab can now be toggled
using the "Toggle Visible" button.
TST: Add tests to support toggle visibility button
ENH: Add callback to toggle category visibility

This callback will hide the categories that are visible and show the
categories that are hidden. With this change we needed a way to refer to
the table with the visibility widgets, hence a new identifier has been
added to it.

Fixes #145.
MAINT: Add note to ChangeLog.md re toggle visible
ENH: Add horizontal line to divide the widgets

An horizontal line now divides the elements under the Visibility and
Scaling tabs, this line separates the "per category" controllers from
the "global controllers".

The test suite was updated accordingly.
ENH: Change button name to Invert Selected

Thanks for the suggestion @teravest
Merge pull request #253 from ElDeveloper/issue-145

Add toggle visibility button
ENH: Fix problems with the layout of the tabs

This is moving to be a more homogeneous layout of all the elements, and
is going to be followed up by a phase of cleaning in the CSS
stylesheet, because at this point is very redundant and useless.
MAINT: Remove redundant classes in stylesheet

A lot of these classes were not being used, or poorly documented or
named in inconistent ways.
STY, MAINT: Cleanup of class names & unused things

Clean up the name of classes to be hyphen separated instead of being
obnoxiously long-named,

Add emperor as a prefix for elements that strongly compose the Emperor
user interface.
BUG, MAINT: Fix non-resizing menu problem

Fix a problem where the menu on the right side was not being resized
correctly, the contents would just simply dissappear.

Rename a few identifiers that had non-informative names.
BUG: Fix problem with layout

The layout wasn't displaying all the contents inside a tab's div because
the height was not set to 100%.
MAINT: Make all tables use the same class

Fixes #254
STY: Remove dead code and whitespace
BUG: Fix Invert Selected button not working

Turns out I removed the id that allows jQuery to fetch the elements
inside the table that contain the visibility information.
DOC: Add mention to the ChangeLog about cleanup
ENH: Use .format instead of %s

This makes the code a bit cleaner, specially for reading
_EMPEROR_FOOTER_HTML_STRING.
TST: Fix tests for layout changes