Close files explicitly.

This should prevent "OSError: Too many open files" errors.
Fix unhelpful "out of memory" errors that used to happen when empty lines are passed to Model.label_sequence.

This function now returns empty string when "lines" argument is empty.
add build files to gitignore
Merge pull request #2 from kmike/close-files

Close files explicitly
Merge pull request #3 from kmike/fix-out-of-memory-error

Fix "out of memory" errors
Merge pull request #4 from kmike/gitignore

add build files to gitignore
add wapiti submodule
remove wapiti
add wapiti
添加submodules
change setup.py add libwapiti/src
add nbest support
auto install submodule
修改package name
Merge pull request #5 from duanhongyi/master

Wapiti as submodule and nbest support
Support for saving compact models
fix not found libwapiti.so in py3k
fix not found libwapiti.so in py3k
pep8 check
pep8 check