fix for force_array behavior

[ThisIsNotTheUserYouAreLookingFor]

Hi there!

This change fixes #46
I did not run the test suite, since I didn't have a lot of time on my hands, I did run with my own test data though.

The behavior has been fixed as follows:

• Instead of a return used next to skip the empty array xpath result
• Initialized result array just before the foreach.
• Added force_array behavior as follows:
  • If the result array size is bigger than one, always set as array
  • If the result array is one and force_array => false take the element and add it as a string to the event

feel free to adjust/throw it against the test suite and let me know what you think!

[jsvd]

merged in 1620c37