Python 2.7 Support

It may run on older versions, but 2.7 is the common distributed version of Python for most stable distros at the moment.

The change was a simple syntax change to split, as it seems Py2 doesn't support passing the maxsplit option as a kwarg.

```bash
(env)nikdoof@vektor:~/dev/esmbc$ python --version
Python 2.7.3
(env)nikdoof@vektor:~/dev/esmbc$ python ./setup.py install >/dev/null
zip_safe flag not set; analyzing archive contents...
esmbc.cli: module references __file__
(env)nikdoof@vektor:~/dev/esmbc$ esmbc
usage: esmbc [-h] [-v] ships [ships ...]
esmbc: error: too few arguments
(env)nikdoof@vektor:~/dev/esmbc$ esmbc hound:3 talwar:2 sabre:1 rupture:1 hurricane:1 tornado:1
Sabre: 43,000m3
Tornado: 216,000m3
Hurricane: 216,000m3
Talwar: 86,000m3
Hound: 84,300m3
Rupture: 96,000m3
Total: 741,300m3
(env)nikdoof@vektor:~/dev/esmbc$ 

(env)nikdoof@vektor:~/dev/esmbc$ python test/test_esmbc.py 
.....
----------------------------------------------------------------------
Ran 5 tests in 0.000s

OK
```