move using statements inside namespace caffe to avoid polluting the whole name space.
neuron_layers.hpp should not need to include leveldb
configure Makefile for CPU-only build
stub out GPU layer methods to crash loudly in CPU-only mode
add guards to drop GPU code in CPU-only mode
collect CUDA includes and calls, separate from CPU-only mode, leave out

- collect CUDA includes in device_alternate.hpp
- add guards for CUDA code
- move GPU code into cu from cpp
- make CUDA includes and libraries conditional in Makefile
- drop CUDA dependency from travis-ci build
switch travis build to CPU-only flag, drop runtestnogpu target
relax benchmark test timing for cheap hardware / CI build
check CPU-only everything, CPU + GPU build with travis
Merge pull request #561 from shelhamer/cpu-only-build

CPU-only build

no GPU, no CUDA, no problem!
compute_image_mean namespace fix.
Merge pull request #716 from Yangqing/dev

Minor Code Cleaning
lint
Merge pull request #718 from Yangqing/dev

More namespace cleaning.
cosmetics: add syntax = proto2
Merge pull request #730 from Yangqing/sweep

cosmetics: add syntax = proto2
use /usr instead of /usr/local for default Python include/lib

This makes the default settings usable with Travis/Ubuntu Python
Travis builds pycaffe
Merge pull request #732 from longjon/travis-pycaffe

Have Travis build pycaffe
Merge branch 'dev' of https://github.com/BVLC/caffe into dev