Fix MAC codes with allelic expansion

[pbashyal-nmdp]

Depending upon whether the expanded alleles for a MAC code contains a : or not, the expansion should be treated differently.

>>> import pyard
>>> ard = pyard.ARD()
>>> ard.expand_mac('B*08:ASXJP')
['B*08:01', 'B*08:19N', 'B*08:109', 'B*08:173']

>>> ard.redux_gl('B*08:ASXJP', 'G')
'B*08:01:01G'
>>> ard.redux_gl('B*08:ASXJP', 'lgx')
'B*08:01'

>>> ard.redux_gl('B*08:AB', 'lgx')
'B*08:01/B*08:02'

Closes #64

[mmaiers-nmdp]

LGTM