Beautification to remove MSVC warning 4800 'int' : forcing value to bool 'true' or 'false'
Merge pull request #59 from mfsv/develop

Beautification to remove MSVC warning 4800...
Merge branch 'develop' of github.com:zeromq/zmqpp into develop
new 4.0 socket/context options, breaking change of add -> add_raw, add_const