ck2cti does not handle species with specific site occupancy

[speth]

Cantera version:

2.3.0 (and current master, 2c3512c)

Expected Behavior:

Surface mechanisms specifying site occupancy for a species should be able to be converted. For example
http://www.detchem.com/mechanisms/05_TWC_PtRh_Chatter2001/sm_C3H6_NO_CO_PtRh_2001_chemkin
which contains in the species definitions the line:

Pt(S) O(S) C3H6(S)/2/ H(S) H2O(S) CO2(S) CO(S) 

which specifies that C3H6(S) takes up 2 sites. This should be translated so that this species has a "size" of 2.

Actual Behavior

The species name is parsed as C3H6(S)/2/, and the mechanism cannot be converted.