add option for lmdb
add tests for lmdb of datalayer (copied from test_data_layer.cpp)
fixed cpplint error
lint
unify test_data_layer tests
unify data layer tests: was copied four times for all combinations of
cpu/gpu and leveldb/lmdb; now just one copy of each test body
add lmdb support for convert_imageset
add lmdb support for compute_image_mean
fix string compare error
Merge pull request #431 from mavenlin/lmdb

Add support for LMDB (LevelDB alternative)