Build error on Fedora 23

[guoxiao]

[ 54%] Built target wangle
[ 55%] Linking CXX executable bin/AcceptorTest
/usr/bin/ld: ../gmock/src/gmock-build/libgmock.a(gtest-all.cc.o): undefined reference to symbol 'pthread_key_delete@@GLIBC_2.2.5'
/usr/lib64/libpthread.so.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
CMakeFiles/AcceptorTest.dir/build.make:102: recipe for target 'bin/AcceptorTest' failed
make[2]: *** [bin/AcceptorTest] Error 1
CMakeFiles/Makefile2:68: recipe for target 'CMakeFiles/AcceptorTest.dir/all' failed
make[1]: *** [CMakeFiles/AcceptorTest.dir/all] Error 2
Makefile:138: recipe for target 'all' failed
make: *** [all] Error 2

[djwatson]

Not sure, looks like some sort of pthreads linking issue? Unfortunately we're only currently testing on ubuntu.

[guoxiao]

I created a PR #19 to fix this problem.