Normalize `.selContainer` return value across browsers.
Introduced `.canSetFocusBeforeNode` and `.canSetFocusInNode`.
Fixed typo.
Fixed typo.
`.nodeAfterSel` throws an exception if selection is not collapsed.

Introduced `.selMustCollapsed`.
NON_CARET_ELEMENTS constant: removed 'th' and added 'thead' and 'colgroup'.
Collapsed selection test: Added a table to the test HTML.
NO_CARET_ELEMENTS: Added 'body' and 'blockquote'.
Set & get collapsed selection test: Exclude editor utility elements.
Set & get collapsed selection test: Assertion string prefix counts nodes.
Collapsed selection set and get: Add 'strong' elements to data.
NON_CONTAINING_ELEMENTS: Added 'col'.
NO_CARET_ELEMENTS: Removed 'body'. Added 'col' and 'tfoot'.
`.nodeAfterSel`: Does not have to be collapsed.
Set & get collapsed selection test: Added an 'i' element to data.
Caret setters renamed: `.setCaretBefore` and `.setCaretIn`.
`.canSetCaretIn` and `.setCaretIn`: Worked around Rangy issue #209.