This makes things *much* faster. We had to make some small code
changes to acheive this (things like directly accessing variables
instead of redirecting through object.__getattribute__), but this
didn't impart PyPy at all (in fact it may actually be faster). New
timings compared to previous commit:

| Operation             | PyPy 2        | Python 2.7    | Python 3.6    |
|---------------------- |-------:       |-----------:   |-----------:   |
| getattr local         |   76ns        |      233ns    |      206ns    |
| setattr local         |   79ns        |      232ns    |      202ns    |
| getattr subclass      |   77ns        |      238ns    |      203ns    |
| setattr subclass      |   75ns        |      238ns    |      204ns    |
| getattr native local  |    2ns        |      139ns    |       73ns    |
| setattr native local  |    2ns        |      168ns    |       98ns    |
| getattr slowdown        	|  38x 	|     1.7x 	|     2.8x 	|
| setattr slowdown        	|  39x 	|     1.7x 	|     2.1x 	|