* Add support for edge style

* Update for TODO: support of solid/dotted/dashed edges (attr = 'style')
* Edge styles are defined as var edgeStyles in parseAttributeList().

* Add example for edge styles

Add an editable example for playing DOT edge styles

* Correct typo and remove TODO description

* Correct typo of filename from 'dotEdgeSytles.html' to
  'dotEdgeStyles.html'.
* Remove TODO description of the issue for edge style