fix(graphs.graph, components.axis) Fixes memory leaks

Fix1: graph.js

Memory leak after destroying the graph(seen in the detached DOM tree) 
![Screen Shot 2013-04-17 at 10 37 29 AM](https://f.cloud.github.com/assets/523368/392771/83fddc62-a786-11e2-9f77-c2487f834cab.png)


After bug fix (Heap profile) 

![Screen Shot 2013-04-17 at 10 40 31 AM](https://f.cloud.github.com/assets/523368/392777/88d24534-a786-11e2-99bc-a03a91565eff.png)

Fix 2: axis.js 
JavaScript handle on g (potentially a memory leak in d3.transform) 

![Screen Shot 2013-04-17 at 10 34 12 AM](https://f.cloud.github.com/assets/523368/392805/d564bf76-a786-11e2-8309-59853d0311ca.png)


After bug fix

![Screen Shot 2013-04-17 at 10 40 31 AM](https://f.cloud.github.com/assets/523368/392795/b628b32e-a786-11e2-8257-dae6f10359c7.png)