binding context menu to tree root
destroy prev defined context menu of the same selector
adding selector option allowing user to control context menu bind element
fix travis warning
If the input value is changed in *edit* callback, the cursor ends up at the end of the text.
Being able to change the node title in *beforeEdit* avoids this.
Changing the input value in *edit* also breaks detection of modification.

My use case is, that I display more information, than should be editable, e.g.:

    Standard-Kettengehänge in Güteklasse 8 | 30* | (37) | [138]

for editing, only:

    Standard-Kettengehänge in Güteklasse 8 | 30*

should be available.
Fix handling of double click in edit extension
I like to keep double click for expanding/collapsing nodes.

Currently the edit extensions prevents the double click event, even if it
is not in option *triggerStart*.
Merge pull request #133 from wolfmanx/fix-edit-dbl-click-handling

Fix handling of double click in edit extension
Merge pull request #132 from wolfmanx/feat-editBefore-title-modification

Allow modification of node title in *beforeEdit* callback
Merge pull request #124 from mcspring/contextMenu-bug

Fix bugs reported in issue #123