<p>Spawn a subshell in the directory of the installed package specified.</p>
<p>If a command is specified, then it is run in the subshell, which then
immediately terminates.</p>
<p>Note that the package is <em>not</em> automatically rebuilt afterwards, so be
sure to use <code>npm rebuild <pkg></code> if you make any changes.</p>
<p>The first element in the 'args' parameter must be a package name. After that is the optional command, which can be any number of strings. All of the strings will be combined into one, space-delimited command.</p>