Casmo API

Pull request replacing #73 to account for asymmetric assemblies
So you suggested doing this: 

In openmoc/compatible/casmo.py:

>      half_width = -1
>      f = open(self._directory + self._filename, 'r')
> +    
> +    #check for symmetry
> +    sym_counter = 0
It looks like this same piece of code is copied and pasted in a couple of different places. Can it be encapsulated into a single routine, perhaps checkSymmetry so that the API doesn't have redundant code?

Which I was also planning on doing. But the thing is, we never used a method we created actually inside the API. 

Like I did create one, but then I got really confused about how to call it. I tried f.checkSymmetry but that didn't work. 

Should I just make it without using "self" at all?

So like, 

def checkSymmetry(f): 

  if blah blah blah:
    self._symmetric = True
  else: 
    self._symmetric = False



and then before every single function (replacing the whole checking for symmetry thing) I just call checkSymmetry(f) ? 

Like

f = open(blah blah blah...)

#check for symmetry

checkSymmetry(f)

if self._symmetric: 

  blah blah blah

else: 

 blah blah blah

....Does that work?