GromacsTopFile parses define value with one extra leading character

When GromacsTopFile reads the `#define` lines, the last character of the variable name got read into the value.  

For instance, the following line:

`#define            tor_ARG_N_CA_CB_CG_m1   0.0   0.0   1 ; PRM 2 3`

got read in as the following:

`top._defines['tor_ARG_N_CA_CB_CG_m1'] = '1   0.0   0.0   1'`.

The leading `1` is not part of the value.  Simply shifting the parser by one character fixes the issue.