Need to initialize local variables

[khushigupta]

I should've sent a PR but anyway - I get the following error when I try and run the code

FailedPreconditionError (see above for traceback): Attempting to use uninitialized value matching_filenames [[Node: matching_filenames/read = Identity[T=DT_STRING, _class=["loc:@matching_filenames"], _device="/job:localhost/replica:0/task:0/cpu:0"](matching_filenames)]]

This is resolved by
init = (tf.global_variables_initializer(), tf.local_variables_initializer())
as mentioned here