Fix assertion failure in Visual Studio

isspace() in Visual Studio only accepts 0 ~ 255. However, the char in Visual
Studio is signed char, thus it causes assertion failure when calling isspace().
To prevent it, we must convert char to unsigned char before calling isspace().
Remove email notification for travis-ci
Move userphrase test cases to test-userphrase.c
Add test cases for auto learn phrase
Add struct tag_PreeditBuf
Replace chiBuf and chiSymbolBuf with preeditBuf