Patch cgi to use ocamlfind to install/remove files

Also adds the required META file

ref #415
No need to set TARGETDIR + use ocamlfind to remove the package
Merge pull request #426 from mirage/master

update cow
sequence 0.3.2 (new combinators)
Merge pull request #428 from c-cube/master

Sequence 0.3.2 released
Merge pull request #425 from rixed/use-ocamlfind-for-cgi

Patch cgi to use ocamlfind to install/remove files
add missing ocamlfind dependency

Additional fix to #425