Do not show error when bundle or npm is not istalled

On Linux I get this to annoying errors:

```
which: no bundle in (/home/asapegin/bin:/home/asapegin/dotfiles/bin:/local/bin:/local/php5/bin:/local/utils:/usr/lib64/mpi/gcc/openmpi/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/usr/games:/usr/lib/mit/bin:/usr/lib/mit/sbin:/local/php5/bin)
which: no npm in (/home/asapegin/bin:/home/asapegin/dotfiles/bin:/local/bin:/local/php5/bin:/local/utils:/usr/lib64/mpi/gcc/openmpi/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/usr/games:/usr/lib/mit/bin:/usr/lib/mit/sbin:/local/php5/bin)
```

Which actually is not errors so I suppress them.