Forward bulkhead spec file has illegal characters on linux

There are two null characters (hex 00) at the end of 4rt700t_spec.json when I check out in linux.  This probably relates to some git/github magic for cross-platform text compatibility.  We need to make sure the process is working across platforms.
```
ska-ccosmos$ ~/git/xija/gui_fit.py 4rt700t_spec.json --stop 2014:125 --days 1600
Traceback (most recent call last):
  File "/home/aldcroft/git/xija/gui_fit.py", line 13, in <module>
    gui_fit.main()
  File "/data/baffin/tom/git/xija/xija/gui_fit.py", line 674, in main
    model_spec = json.load(open(opt.filename, 'r'))
  File "/proj/sot/ska/arch/x86_64-linux_CentOS-6/lib/python2.7/json/__init__.py", line 278, in load
    **kw)
  File "/proj/sot/ska/arch/x86_64-linux_CentOS-6/lib/python2.7/json/__init__.py", line 326, in loads
    return _default_decoder.decode(s)
  File "/proj/sot/ska/arch/x86_64-linux_CentOS-6/lib/python2.7/json/decoder.py", line 363, in decode
    raise ValueError(errmsg("Extra data", s, end, len(s)))
ValueError: Extra data: line 422 column 2 - line 422 column 4 (char 12231 - 12233)

ska-ccosmos$ od -a 4rt700t_spec.json  | tail
0027500  sp  nl  sp  sp  sp  sp  sp  sp  sp  sp  sp  sp  sp  sp   "   m
0027520   i   n   "   :  sp   1   0   0   .   0   ,  sp  nl  sp  sp  sp
0027540  sp  sp  sp  sp  sp  sp  sp  sp  sp   "   n   a   m   e   "   :
0027560  sp   "   t   a   u   "   ,  sp  nl  sp  sp  sp  sp  sp  sp  sp
0027600  sp  sp  sp  sp  sp   "   v   a   l   "   :  sp   1   4   9   .
0027620   4   8   6   5   8   3   1   8   8   8   7   1   9   8  nl  sp
0027640  sp  sp  sp  sp  sp  sp  sp   }  nl  sp  sp  sp  sp   ]   ,  sp
0027660  nl  sp  sp  sp  sp   "   t   l   m   _   c   o   d   e   "   :
0027700  sp   n   u   l   l  nl   } nul nul
```