title: Could NOT find CURL (missing: CURL_LIBRARY CURL_INCLUDE_DIR) on CMake
body: <p>I'm trying to use api.ai C++ library on Windows 7.
  (<a href="https://github.com/api-ai/libapiai" rel="noreferrer">https://github.com/api-ai/libapiai</a>)
  But i can not configuring that files..</p>
  
  <p>I installed CMake and MinGW.</p>
  
  <p>in build directory 
  -> cmake .. -G "MinGW Makefiles" 
  -> Error !!</p>
  
  <p>===>>> error is below &lt;&lt;&lt;</p>
  
  <pre><code>CMake Error at C:/Program Files (x86)/CMake/share/cmake-3.4/Modules/FindPackageHandleStandardArgs.cmake:148 (message):
    Could NOT find CURL (missing: CURL_LIBRARY CURL_INCLUDE_DIR)
  Call Stack (most recent call first):
    C:/Program Files (x86)/CMake/share/cmake-3.4/Modules/FindPackageHandleStandardArgs.cmake:388 (_FPHSA_FAILURE_MESSAGE)
    C:/Program Files (x86)/CMake/share/cmake-3.4/Modules/FindCURL.cmake:61 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
    CMakeLists.txt:45 (find_package)
  </code></pre>
  
  <p>I don't know how can I solve.
  what is curl_library? 
  I can use that on Windows 7? not linux/unix etc..</p>