only install header files necessary for tools
only install header files necessary for tools

Summary: My previous patch would install all header files. In practice, we only want the header files that would be necessary to build a tool (using libtool). This patch also fixes a bug where sparta is installed in `include/redex/include` instead of `include/redex/sparta`.

Reviewed By: thezhangwei

Differential Revision: D26116398

fbshipit-source-id: 9ec227d05dadb38684666d402a9bd88314296da6

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex