Try to install on os x

Related to #30

made some changes, and end-up with:

```
Sites/onion/build[master]% cmake ..
-- The C compiler identification is GNU
-- The CXX compiler identification is GNU
-- Checking whether C compiler has -isysroot
-- Checking whether C compiler has -isysroot - yes
-- Checking whether C compiler supports OSX deployment target flag
-- Checking whether C compiler supports OSX deployment target flag - yes
-- Check for working C compiler: /usr/bin/gcc
-- Check for working C compiler: /usr/bin/gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Checking whether CXX compiler has -isysroot
-- Checking whether CXX compiler has -isysroot - yes
-- Checking whether CXX compiler supports OSX deployment target flag
-- Checking whether CXX compiler supports OSX deployment target flag - yes
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Using libev as poller
Gnutls not found. SSL support is not compiled in.
-- pthreads found. Threading support is compiled in.
-- libxml2 found. WebDAV support is compiled in.
-- libpng found. png support is compiled in at extras.
-- libcairo found. Adding cairo examples. /usr/X11R6/lib/libcairo.dylib
-- curl found. Some extra test are compiled.
librt not found. Systemd support is not compiled in.
-- Prepared for packaging
libev found at /usr/local/lib/libev.dylib
INFOCompiling WebDAV support
Found include files static.h;exportlocal.h;auth_pam.h;opack.h;path.h;webdav.h;internal_status.h
Found include files png.h
Found include files block.h;codecs.h;dict.h;handler.h;http.h;https.h;listen_point.h;log.h;mime.h;onion.h;poller.h;request.h;response.h;sd-daemon.h;server.h;sessions.h;shortcuts.h;types.h;types_internal.h;url.h;websocket.h
Found include files onion.hpp;dict.hpp;request.hpp;response.hpp;url.hpp;handler.hpp;extrahandlers.hpp
CMake Warning at examples/CMakeLists.txt:11 (message):
  Oterm without authentication support! May be very unsecure.


CMake Warning at examples/CMakeLists.txt:16 (message):
  Some examples are disabled as you dont have PAM: otop, basic, fileserver.


-- Configuring done
-- Generating done
-- Build files have been written to: /Users/apple/Sites/onion/build
Sites/onion/build[master]% make
Scanning dependencies of target onion
[  1%] Building C object src/onion/CMakeFiles/onion.dir/onion.c.o
[  2%] Building C object src/onion/CMakeFiles/onion.dir/codecs.c.o
[  3%] Building C object src/onion/CMakeFiles/onion.dir/dict.c.o
[  3%] Building C object src/onion/CMakeFiles/onion.dir/request.c.o
[  4%] Building C object src/onion/CMakeFiles/onion.dir/response.c.o
[  5%] Building C object src/onion/CMakeFiles/onion.dir/handler.c.o
[  6%] Building C object src/onion/CMakeFiles/onion.dir/log.c.o
[  7%] Building C object src/onion/CMakeFiles/onion.dir/sessions.c.o
[  7%] Building C object src/onion/CMakeFiles/onion.dir/shortcuts.c.o
[  8%] Building C object src/onion/CMakeFiles/onion.dir/block.c.o
[  9%] Building C object src/onion/CMakeFiles/onion.dir/mime.c.o
[ 10%] Building C object src/onion/CMakeFiles/onion.dir/url.c.o
[ 11%] Building C object src/onion/CMakeFiles/onion.dir/poller_libev.c.o
[ 11%] Building C object src/onion/CMakeFiles/onion.dir/listen_point.c.o
[ 12%] Building C object src/onion/CMakeFiles/onion.dir/request_parser.c.o
[ 13%] Building C object src/onion/CMakeFiles/onion.dir/http.c.o
[ 14%] Building C object src/onion/CMakeFiles/onion.dir/websocket.c.o
Linking C shared library libonion.dylib
[ 14%] Built target onion
Scanning dependencies of target onion_static
[ 15%] Building C object src/onion/CMakeFiles/onion_static.dir/onion.c.o
[ 16%] Building C object src/onion/CMakeFiles/onion_static.dir/codecs.c.o
[ 17%] Building C object src/onion/CMakeFiles/onion_static.dir/dict.c.o
[ 17%] Building C object src/onion/CMakeFiles/onion_static.dir/request.c.o
[ 18%] Building C object src/onion/CMakeFiles/onion_static.dir/response.c.o
[ 19%] Building C object src/onion/CMakeFiles/onion_static.dir/handler.c.o
[ 20%] Building C object src/onion/CMakeFiles/onion_static.dir/log.c.o
[ 21%] Building C object src/onion/CMakeFiles/onion_static.dir/sessions.c.o
[ 21%] Building C object src/onion/CMakeFiles/onion_static.dir/shortcuts.c.o
[ 22%] Building C object src/onion/CMakeFiles/onion_static.dir/block.c.o
[ 23%] Building C object src/onion/CMakeFiles/onion_static.dir/mime.c.o
[ 24%] Building C object src/onion/CMakeFiles/onion_static.dir/url.c.o
[ 25%] Building C object src/onion/CMakeFiles/onion_static.dir/poller_libev.c.o
[ 25%] Building C object src/onion/CMakeFiles/onion_static.dir/listen_point.c.o
[ 26%] Building C object src/onion/CMakeFiles/onion_static.dir/request_parser.c.o
[ 27%] Building C object src/onion/CMakeFiles/onion_static.dir/http.c.o
[ 28%] Building C object src/onion/CMakeFiles/onion_static.dir/websocket.c.o
Linking C static library libonion_static.a
[ 28%] Built target onion_static
Scanning dependencies of target onion_handlers
[ 28%] Building C object src/onion/handlers/CMakeFiles/onion_handlers.dir/static.c.o
[ 29%] Building C object src/onion/handlers/CMakeFiles/onion_handlers.dir/exportlocal.c.o
[ 30%] Building C object src/onion/handlers/CMakeFiles/onion_handlers.dir/opack.c.o
[ 31%] Building C object src/onion/handlers/CMakeFiles/onion_handlers.dir/path.c.o
[ 32%] Building C object src/onion/handlers/CMakeFiles/onion_handlers.dir/internal_status.c.o
[ 32%] Building C object src/onion/handlers/CMakeFiles/onion_handlers.dir/webdav.c.o
Linking C shared library libonion_handlers.dylib
[ 32%] Built target onion_handlers
Scanning dependencies of target onion_handlers_static
[ 33%] Building C object src/onion/handlers/CMakeFiles/onion_handlers_static.dir/static.c.o
[ 34%] Building C object src/onion/handlers/CMakeFiles/onion_handlers_static.dir/exportlocal.c.o
[ 35%] Building C object src/onion/handlers/CMakeFiles/onion_handlers_static.dir/opack.c.o
[ 36%] Building C object src/onion/handlers/CMakeFiles/onion_handlers_static.dir/path.c.o
[ 36%] Building C object src/onion/handlers/CMakeFiles/onion_handlers_static.dir/internal_status.c.o
[ 37%] Building C object src/onion/handlers/CMakeFiles/onion_handlers_static.dir/webdav.c.o
Linking C static library libonion_handlers_static.a
[ 37%] Built target onion_handlers_static
Scanning dependencies of target onion_extras
[ 38%] Building C object src/onion/extras/CMakeFiles/onion_extras.dir/png.c.o
Linking C static library libonion_extras.a
[ 38%] Built target onion_extras
Scanning dependencies of target onioncpp
[ 39%] Building CXX object src/bindings/cpp/CMakeFiles/onioncpp.dir/handler.cpp.o
[ 39%] Building CXX object src/bindings/cpp/CMakeFiles/onioncpp.dir/extrahandlers.cpp.o
Linking CXX shared library libonioncpp.dylib
Undefined symbols for architecture x86_64:
  "_onion_request_get_path", referenced from:
      Onion::Request::path() constin extrahandlers.cpp.o
  "_onion_shortcut_response_file", referenced from:
      Onion::StaticHandler::operator()(Onion::Request&, Onion::Response&)in extrahandlers.cpp.o
  "_onion_handler_new", referenced from:
      Onion::Handler::Handler()in handler.cpp.o
      Onion::Handler::Handler()in handler.cpp.o
  "_onion_shortcut_response", referenced from:
      onion_handler_call_operator(void*, onion_request_t*, onion_response_t*)  in handler.cpp.o
  "_onion_log", referenced from:
      onion_handler_call_operator(void*, onion_request_t*, onion_response_t*)  in handler.cpp.o
  "_onion_response_write", referenced from:
      Onion::Response::write(char const*, int)in handler.cpp.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make[2]: *** [src/bindings/cpp/libonioncpp.dylib] Error 1
make[1]: *** [src/bindings/cpp/CMakeFiles/onioncpp.dir/all] Error 2
make: *** [all] Error 2
```