Fix bfs_client return value (baidu#775)

(baidu#754)

Fix a Spelling error SDk to SDK (baidu#737)

(baidu#580)

Add file lock doc (baidu#657)

(baidu#622）Add file lock design doc

fix gcc error when using fuse (baidu#633)

Merge pull request baidu#553 from yvxiang/show_tag

Show chunkserver tag is SysStat baidu#551

Merge pull request baidu#534 from baidu/master

Merge master

Merge pull request baidu#515 from yvxiang/write

Hold lock in Block::Write

Merge pull request baidu#511 from yvxiang/seek

Support seek write file

Merge pull request baidu#490 from yvxiang/lock

Add lock

Merge pull request baidu#393 from lylei/ha.fix

fix slave safemode