modified the function ica_select_brain_responsefunction

The new function can make raw data related with special events. 
@pravsripad I test the 'rstrip function'
```ruby
fn_clean
Out[10]: '/home/qdong/freesurfer/subjects/101611/MEG/101611_audi_cued,bp1-45Hz,ar-raw.fif'
 fn_clean.split('-raw.fif')[0]
Out[11]: '/home/qdong/freesurfer/subjects/101611/MEG/101611_audi_cued,bp1-45Hz,ar'
fn_clean.rstrip('-raw.fif')
Out[12]: '/home/qdong/freesurfer/subjects/101611/MEG/101611_audi_cued,bp1-45Hz,'
```
the 'rstrip' function will miss 'ar', and then will cause errors from the path of the ica and txt file. I prefer to use the 'split' function.