strings: Include SPACE in the regexp in strings

The previous regular expression that was used in strings didn't match
the SPACE character. This commit makes strings behave a little more like
GNU strings.

_________
Example
```
vault@viper:~/Code/viper [master]$ cat /tmp/roz
This is a test
to see how the new regex will
react!
```

Old behaviour:
```
viper roz > strings -a                                                                                                                     
This
test
regex
will
react
```

New behaviour:
```
viper roz > strings -a                                                      
This is a test
to see how the new regex will
react
```