Try to cythonize when Cython is installed

[slaypni]

Change to use

• Cython to compile .pyx
• GCC to compile .cpp
• Pure Python

if available when running

python setup.py install

[zhahaoqiang]

Hello
when i run python setup.py install
i get a erro or warning
building 'fastdtw._fastdtw' extension
setup.py:81: UserWarning: compilation failed. Installing pure python package
warnings.warn(reason+'compilation failed. Installing pure python package')
how can i fix it.
thanks a lot

[slaypni]

@zhahaoqiang Cloud you paste the entire error message? Please also take a look at #13