* Add arrowhead support
As described in TODO, dotparser.js does not support 'arrowhead'
attribubte of edge.
This update is for adding 'dot' and 'tee'(bar) styles.
* Add example for arrow styles
* Add box arrowhead
To support box arrowhead of graphviz, add Box endpoint class in
EndPoints.js and box attribute in dotparser.js.
* Add diamond arrowhead
To support diamond arrowhead of graphviz, add Diamond endpoint
class in EndPoints.js and diamond attribute in dotparser.js.
* Add crow arrowhead
To support crow arrowhead of graphviz, add Crow endpoint
class in EndPoints.js and crow attribute in dotparser.js.
* Add normal arrowhead
To support normal arrowhead of graphviz, add Triangle endpoint
class in EndPoints.js and normal attribute in dotparser.js.
* Add curve arrowhead
To support curve arrowhead of graphviz, add Curve endpoint
class in EndPoints.js and curve attribute in dotparser.js.
* Add inverted curve arrowhead
To support inverted curve arrowhead of graphviz, add InvertedCurve
endpoint class in EndPoints.js and icurve attribute in
dotparser.js.
* Add vee arrowhead
To support vee arrowhead of graphviz, add Vee endpoint class in
EndPoints.js and vee attribute in dotparser.js.
* Add arrowhead examples
* Fix bug for accessing null attribute
In createEdge(), accessing 'attr' causes an error if the edge has no
attribute and the value is null.
This update fixes bug for accessing null 'attr'.
* Update description for arrows.to.type option
Add followingn options for 'arrows.to.type'.
* box
* crow
* curve
* diamond
* inv_curve
* triangle
* inv_triangle
* vee
* Update edgeStyle example for arrow types
Add arrow types for the example.
'box', 'crow', 'curve', 'inv_curve', 'diamond', 'triangle',
'inv_triangle', 'vee'