Fixed output issues webith websearch plugin.

- if user has rm set as an alias to 'rm -i' user is prompted to whether to
  remove the nohup.out file.

 $ ddg fools
	nohup: ignoring input and appending output to ‘nohup.out’
	rm: remove regular empty file ‘nohup.out’?

- if output redirected to a file nohup will not create nohup.out and rm is
  unecessary.
Merge pull request #3397 from peteches/master

Fixed output issues webith websearch plugin.