updated "performance.pl"

[Su]

Hello All,

Due to lack of instruction for "performance.pl", inside the script, I
added a brief instruction (e.g. how to use, format of your keywords,
and also where to change if you want to use it for other data other
than test data).
FYI, current version of "performance.pl" is meant for test data.

The output of the script looks like :

correct keyword = XXX
-------------------------------------------------------------------------------------
[AUTHOR.STEM.FINAL] Match_Precision_Recall_Fscore
Top 05: XX XX% XX% XX%
Top 10: XX XX% XX% XX%
Top 15: XX XX% XX% XX%
correct keyword = XXX
-------------------------------------------------------------------------------------
[READER.STEM.FINAL] Match_Precision_Recall_Fscore
Top 05: XX XX% XX% XX%
Top 10: XX XX% XX% XX%
Top 15: XX XX% XX% XX%
correct keyword = XXX
-------------------------------------------------------------------------------------
[COMBINED.STEM.FINAL] Match_Precision_Recall_Fscore
Top 05: XX XX% XX% XX%
Top 10: XX XX% XX% XX%
Top 15: XX XX% XX% XX%

"correct keyword" is the number of keywords in the answer file

Thank you.