Fix switch layer attribute name

Fixed some ssd bugs.

Refactor operator python test framework and add sum operator

Adapting to the BatchNorm structure to support 3D data

Adaptive data structure for switch order layer

fix batch_norm parameter share

Design doc: operator based parameter server.

Fix name in test_lookup_table

Add axis for `mul_op` and `rowwise_add_op`

rewrite backward graph

Update functions_operators_layers.md

Fix android-16 compile.

Fix error on TravisCI

It seems that Travis change the running image. The /usr/local/ is
not writable in new images. Use `sudo` for pip to resolve this.