Bad Memory Leak

[KatieWoe]

For phetsims/qa#216
Start: 17.5 MB
1 min: 128 MB
2 min: 231 MB
3 min: 334 MB
4 min: 441 MB
5 min: crash before heap snapshot can finish.
Will try test on published version per request of @jbphet

[KatieWoe]

With published version:
Start: 13 MB
1 min: 14.8 MB
2 min: 15.5 MB
3 min: 15.9 MB
4 min: 16.1 MB
5 min: 16.5 MB

[KatieWoe]

@jbphet requested the test be done on recently published States of Matter.
Start: 27.2
1 min: 56.6
2 min: 74.9
3 min: 94.2
4 min: 119
5 min: 137

[jbphet]

I did a memory analysis and found the leaks. There were three nodes for which there were no dispose functions, so they have been added. Kinda a lame of me to have missed these, but it's great that QA ran this test and identified the problem.

Running a RequireJS version of Atomic Interactions, I now see the following memory heap size:

Time (minutes)	Memory Usage (MB)
0	17.3
1	22.6
2	22.8
3	24.5
4	25.3
5	25.6
6	25.5
7	25.7
8	26.0
9	26.2
10	26.2

This is a pretty reasonable profile. The memory is increasing very gradually, and decreases between minutes 5 and 6, and holds steady between minutes 9 and 10. I did some comparisons between the heap snapshots, and there was nothing obvious from the sim that was leaking. If there is a slow leak, it's probably somewhere in common code, and it's not enough to cause any problems.

Bottom line: I think this is now fixed.