Update travis script
Add prefix expansion command
vim: "dwim" / prefix expansion on :Locate
vim: dwim on empty completion, g:merlin_dwim_completion setting
Simplify incremental parsing interface

Functional proof of concept, more code can be dropped
Remove dead code from merlin_parser
Simplify type checker
Work only on 4.02.1
Update TODO
Rename Makefile.ocamlmakefile -> Makefile.merlin
Travis: use only 4.02
PoC PPX
PPX: add support for caching cookies