Revert "Use child_process.exec() instead of spawn() in FileFinder"

child_process.exec kills the subprocess after 200 kB of stdout, which is not a high enough threshold in many cases: http://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback.

This reverts the lib/FileFinder.js changes in commit 40b39985efa7ffb084207dc1a8c1b86bd2c0725c and bumps the package version number.
Merge pull request #10 from spicyj/no-exec

Revert "Use child_process.exec() instead of spawn() in FileFinder"