Ported to libc++.
Merge pull request #7 from gwtnb/libc++

Ported to libc++.
Revert "Merge pull request #7 from gwtnb/libc++"

This reverts commit 91a4656e601e2a9759e19e90cbfaa037c290ba44, reversing
changes made to eea93558b154dffdb279606fa421f2c27a384c4e.

Commit 91a4656e601e2a9759e19e90cbfaa037c290ba44 breaks Jubatus build.
Fix link option to msgpack
Insert atack.h in test to distribution file
Fix code style
Stop using -O4.

-O4 is undocumented in gcc, and ignored by intel compiler.
Remove unused m4 file.
Add -pthread.
add remove_session method to session_pool
Merge pull request #11 from gwtnb/stop-using-o4

Stop using -O4.
Merge pull request #14 from kmaehashi/remove-from-session-pool

add remove_session method to session_pool
Merge pull request #12 from gwtnb/pthread

Add -pthread.
Merge pull request #10 from jubatus/fix-makefile-for-test

Fix makefile for test
bump version
Merge branch 'release/0.4.3' into develop