Shorten image names.
Open options in a new tab.

Previously, clicking on "options" or "about" link in the question GUI
would open the relevant page in the same window and affect user's
navigation. Now they open in a new tab with target="_blank".
On preferences update, notify all option pages.

If the user has multiple "options" pages opened, modifications in
one of them will now be reflected in others.
Fix flickering iframe by pre-setting border width.
Improve options handling.

- Options now listen to updateUserPreferences event;
- Improve navigation between faux-tab contents;
- Override unnecessary transition when opening options with "#about" hash;
- Some refactoring.
Merge branch 'better-options' into develop

Improves options handling and GUI, fixes bugs.
Add margin property for iframe.
Prohibit outline of :target-ed navigation elements.
Less nesting levels.
Simplify html structure.
Adjust for id change on the info element.
Realign the question elements and refactor.
Limit line breaks on whitespace only in answers.
Add timer progress indicator.
Merge branch 'interface-realign' into develop
Update README for v0.6

- Provide direct links for beta and dev releases;
- Add changelog for v0.6
Merge branch 'develop' for 0.6 release.

- Interface improvements;
- Code refactoring;
- Bug fixes;

Closes #5, closes #6.