Layers

Add more tensorflow layers
- tf.nn.conv2d
- tf.nn.depthwise_conv2d
- tf.nn.separable_conv2d
- tf.nn.conv2d_transpose
- tf.nn.avg_pool
- tf.nn.max_pool
- tf.nn.max_pool_with_argmax
Have a look here https://www.tensorflow.org/versions/r0.8/api_docs/python/contrib.layers.html