SVG: sigma.renderer.svg.js changes

- add upNode and downNode events
- hide/show hover elements when the mouse is pressed on a node or
  released from a node
- checks if the hover elements exist before adding/remove them
Fix minor issues

- check e.data.node instead of hoveredNode
- prevent update if hovering is disabled such as mouse down and up events
fix closure lint and jshint errors
SVG: diable all mouse interactions with all label and hover elements

When dragging the graph or a node, any mouse movement that interacts
with label and hover elements can cause some really weird behaviors to
the graph.

pointer-events are not supported for IE 9 and IE 10, so a polyfill
library is added.
Fixed closure lint and jshint errors
SVG: dragNode not capturing any mouse events
Add bower.json file
SVG: issues with labels

- label contents don't get updated
- hover area still gets created if the node doesn't have a label
Fix closure lint error
SVG: dragNode not capturing any mouse events
SVG: diable all mouse interactions with all label and hover elements

When dragging the graph or a node, any mouse movement that interacts
with label and hover elements can cause some really weird behaviors to
the graph.

pointer-events are not supported for IE 9 and IE 10, so a polyfill
library is added.
SVG: sigma.renderer.svg.js changes

- add upNode and downNode events
- hide/show hover elements when the mouse is pressed on a node or
  released from a node
- checks if the hover elements exist before adding/remove them
Add bower.json file
Fix minor issues

- check e.data.node instead of hoveredNode
- prevent update if hovering is disabled such as mouse down and up events
add label alignment settings

- add label alignment settings
- fix jslint errors
- when zoom in/out, adjust hovered circle for the node accordingly
- when use "center" setting, the rectangle area will not be displayed
- when use "inside" setting, default setting will be used if the width
  of the label is larger than the hovered circle.
Merge branch 'fixLabelUpdate' into mysigma
Merge branch 'labelUpdates' into mysigma
Merge branch 'labels' into mysigma
Merge branch 'newEvents' into mysigma

Conflicts:
	src/misc/sigma.misc.bindDOMEvents.js
	src/renderers/sigma.renderers.svg.js
Merge branch 'pointerEvents' into mysigma

Conflicts:
	src/utils/pointer_events_polyfill.js