First stab at supporting fixed-size C array assignment

*This PR is currently a work-in-progress.*

Allows code like:

    cdef int a[10]
    cdef object o = range(10)
    a = o

The list's contents are copied into the fixed array.

Currently supports:

```python
def convert_int(o):
    cdef int a[10]
    a = o
    print a[0], a[9]

def convert_float(o):
    cdef float a[10]
    a = o
    print a[0], a[9]
```

Currently unsupported, working on implementing:

* assignment at declaration: `cdef int a[10] = obj`
* extensive error testing and handling edge cases
* automatic conversion from array back to Python object
    * what type?  `array.array`?
* cleaning up and improving tempita templates