Added AVL extension, red-black tree and stack to JSAV extras.
Merge pull request #127 from X455u/extras

Thanks for these! (AVL extension, Red-Black Tree and Stack)
FIxed bug in setting pointer target to null
Documented test and tries options for randomization functions
Changed heap tree swap to use effects.swapValue to fix  few issues
Changed heap indexing to start from zero
Proper inheritance of all JSAV objects (closes #120)
Added class toggling functions to Label
Small 'box' shown below pointers; automatically add jsavnullpointer class to null pointers
Added example of setting pointer target to null
Added subtle shadow to nodes (closes #125)
Grade button not shown in continuous grading mode (see #94)
Undirected graphs now only have max one edge for each pair of nodes (see #100)
Updated graph tests to match previous change (see #100)
Fixed issue with graph/list/pointer arrow colors by siwtching to custom version of Raphael (see #96)
Changelog and documentation updated in preparation for 0.7 release
Pointer position can now be fixed.
Added an example of a fixed pointer
Fixed a bug in moving childnode from one node to another
Fixed node moving bug for Binarytree as well; added tests for these bugs