text: Title: python 3 incompatible when use map function
  Body: https://github.com/tflearn/tflearn/blob/master/tflearn/layers/core.py#L662
  `    x = map(lambda t: tf.reshape(t, [-1, 1]+utils.get_incoming_shape(t)[1:]), x)
  `
  cause a compatible issue when using python3.  should change to
  `x = list(map(lambda t: tf.reshape(t, [-1, 1]+utils.get_incoming_shape(t)[1:]), x))`
  
  here is the exception I got:
  
  ...
    File "/anaconda/lib/python3.5/site-packages/tflearn/layers/core.py", line 654, in time_distributed
      return tf.concat(1, x)
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/ops/array_ops.py", line 1077, in concat
      return identity(values[0], name=scope)
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/ops/gen_array_ops.py", line 1424, in identity
      result = _op_def_lib.apply_op("Identity", input=input, name=name)
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/framework/op_def_library.py", line 493, in apply_op
      raise err
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/framework/op_def_library.py", line 490, in apply_op
      preferred_dtype=default_dtype)
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/framework/ops.py", line 669, in convert_to_tensor
      ret = conversion_func(value, dtype=dtype, name=name, as_ref=as_ref)
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/framework/constant_op.py", line 176, in _constant_tensor_conversion_function
      return constant(v, dtype=dtype, name=name)
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/framework/constant_op.py", line 165, in constant
      tensor_util.make_tensor_proto(value, dtype=dtype, shape=shape, verify_shape=verify_shape))
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/framework/tensor_util.py", line 441, in make_tensor_proto
      tensor_proto.string_val.extend([compat.as_bytes(x) for x in proto_values])
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/framework/tensor_util.py", line 441, in <listcomp>
      tensor_proto.string_val.extend([compat.as_bytes(x) for x in proto_values])
    File "/anaconda/lib/python3.5/site-packages/tensorflow/python/util/compat.py", line 65, in as_bytes
      (bytes_or_text,))
  TypeError: Expected binary or unicode string, got <map object at 0x159ca0630>