Add: grep option for bundle open 

allows the use of a '--grep' option to use bundle open.
 
```
$ bundle open active --grep 
1 : activesupport
2 : activemodel
3 : active_reload
4 : activerecord
5 : activeresource
6 : interactive_rspec
0 : - exit -
>  2
<< open activerecord  >> 
```