Fix config.xml path
Fix Ember.js spelling - based on homepage's title
Make style of tag attribute change match

Removed closing tag to match style of <body> tag change on
docs/guide/starting.md page.
Fix header class of guide's application

Every other code listing of guide's application uses bar-dark as header
class. This class is also used on the screenshots.
Remove unused 'Edit tasks' button
Guide's application, fix task creation

Previous version has two problems:
1) It keeps previously entered task title in the new task form,
2) It adds only single task to the list, because form operates on single
instance of task.

Current version is based on example with projects.
Make style of "New task" match other examples
Merge pull request #118 from ciastek/guide-fixes

Guide fixes