Fix install_script to make a directory if the destination doesn't exist.
Fix install_script to make a directory if the destination doesn't exist.

It caused 'No such file or directory' error if ROSWELL_INSTALL_DIR is not the same as ROSWELL_DIR
because there's no ~/.roswell/bin directory by default.

pradhyu/roswell,roswell/roswell,amarie-formation/roswell,kubov/roswell,JulienBoubechtoulaAmabis/roswell,pradhyu/roswell,guicho271828/roswell,roswell/roswell,snmsts/roswell,kubov/roswell,kubov/roswell,pradhyu/roswell,amarie-formation/roswell,snmsts/roswell,guicho271828/roswell,JulienBoubechtoulaAmabis/roswell,JulienBoubechtoulaAmabis/roswell,amarie-formation/roswell,JulienBoubechtoulaAmabis/roswell,guicho271828/roswell,pradhyu/roswell,snmsts/roswell,snmsts/roswell,guicho271828/roswell,amarie-formation/roswell,roswell/roswell,roswell/roswell,JulienBoubechtoulaAmabis/roswell,kubov/roswell