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
Modify chewing_set_maxChiSymbolLen to fix #50

The original chewing_set_maxChiSymbolLen adds ZUIN_SIZE when determine
if auto commit is needed. It is ambiguous because user expects the value
set by chewing_set_maxChiSymbolLen is the maximum character/symbol in
preedit buffer. By removing ZUIN_SIZE, the behavior is the same as user
expectation.
Store index in word for stable sort

In FreeBSD, the compare function for qsort() cannot use address to
implement stable sort because the address passed to compare function is
not the original one. Thus we change to use index instead of address to
implement stable sort.

See [1] for more information.

[1] https://groups.google.com/d/msg/chewing-devel/cUovLo0zGuc/-t2S3OfMDcYJ