Added 2 new shades of yellow, modified ace-jump-mode and org headline and block faces

* Updated how the headings, #+BEGIN_SRC, #+END_SRC, inbetween source code blocks look in org mode
![clipboard01](https://cloud.githubusercontent.com/assets/3578197/3334263/10e241e6-f7fd-11e3-96c2-fe32d64ec06a.png)

* Earlier ace-jump faces made it difficult to read the window numbers when using ace-window package. The brighter yellow face highlights that. This yellow color is used only when user's attention is required; doesn't break the general low-contrast theme.
![clipboard02](https://cloud.githubusercontent.com/assets/3578197/3334264/10e2e614-f7fd-11e3-8dc6-3f1e2d0da8fc.png)

* The same yellow theme appears in regular ace-jump uses and doesn't look bad 
![clipboard03](https://cloud.githubusercontent.com/assets/3578197/3334262/10e2256c-f7fd-11e3-99c1-a42ec033e63c.png)