gtags本身並不支援Python
但是有個透過plugin可以加上python syntax highlighting來生成正確的tag
用法：
$ sudo pip install Pygments
$ git clone https://github.com/yoshizow/global-pygments-plugin.git
$ cd global-pygments-plugin
$ ./reconf.sh
$ ./configure
$ make
$ sudo make install
$ cp sample.globalrc ~/.globalrc
參考資料：
[1] https://stackoverflow.com/questions/5661485/how-to-add-python-plug-in-to-gnu-global
[2] https://github.com/yoshizow/global-pygments-plugin
