Fix negative frequency problem

Closed #75
Add macros for logging
Log insert/update userphrase
Refactoring Discard1
Replace IsIntervalInside with PhraseIntervalContain
Do not check phrase longer than MAX_PHRASE_LEN

Part of #73
fix typo in testhelper.c

Signed-off-by: ChangZhuo Chen (陳昌倬) <czchen@gmail.com>
add performamce into .gitignore

Signed-off-by: ChangZhuo Chen (陳昌倬) <czchen@gmail.com>