Fixed some typos and added missing import

Fixed two typos, but now it produces a segmentation fault. 

```
$ python massage_mei.py /Users/zoltan/Documents/DuChemin/summer14/DC01_MEI_files/DC0101E.xml 
WARNING:root:Warning: more than one <staffGrp>; using first occurrence.
Python(47544,0x7fff746b6310) malloc: *** error for object 0x7fe4d2111370: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap: 6
```