Fix deprecated methods of Chainer 1.24.0

[massongit]

I fixed deprecated methods of Chainer 1.24.0: chainer.cuda.get_device and bi_lstm.BiLSTM_CNN_CRF.zerograds (chainer.Chain.zerograds).

[aonotas]

Thank you for your great PR!

[aonotas]

Could you fix your code to define own chainer util functions like followings:

# util_chainer.py
def my_cuda_get_device(cuda, device_id):
    if version < '2.0':
        cuda.get_device(device_id).use()
    else:
        # v2.0
        cuda.get_device_from_id(device_id).use()


def my_cleargrads(net):
    if version < '2.0':
        net.zerograds()
    else:
        # v2.0
        net.cleargrads()

# main.py
from util_chainer import my_cuda_get_device, my_cleargrads

[aonotas]

if you fix your code, I will merge it!
Thank you for your help :)

[massongit]

Thank you for your comments!

I think it is unnecessary to define own chainer util functions.
As the reason:

• This tool supports Chainer 2.1.0 and 1.24.0.
• chainer.cuda.get_device was deprecated on Chainer 1.23.0 (earlier Chainer 1.24.0).
• chainer.Chain.zerograds was deprecated on Chainer 1.15.0 (earlier Chainer 1.24.0).

[aonotas]

OK! Thank you for your help :)
I will merge your PR.