1. add timer. (to be continue.)
1. add util
2. add lib and gtest
1. add clock
2. add cond
3. add context
4. add utime
5. complete timer
1. finish feature of timer
2. compile and link ok
3. test basic function of timer ok
1. add new file
1. remove odd files
1. finish feature of disk initial
2. test basic function of disk initial ok
Merge branch 'master' into wip-stream-map

Conflicts:
	test/logger_test.cc
Merge branch 'master' into wip-stream-map