Emacs: fix merlin-type-region
locate: better handling of packed modules

Get rid of the cwd-related heuristic.
The case described in #284 should be handled.
locate: reset fallback on new calls (bugfix)
std: String.init doesn't exist pre 4.02
locate: try to use source digest to select source file before using heuristic

Thanks samoht for the suggestion on #284
locate: small fix for ad67917
vim: ugly-hack: replace ' by ` when populating the loclist
locate: follow-up on the previous "fix", more precise analysis of context
locate: use context to locate type or value appropriatly
Handles the last point of #308

Also, minor code cleanup.
vim: add a dump_to_file function
Work only on 4.02.1
Update TODO
vim completion: synchronize before completion
Rename Makefile.ocamlmakefile -> Makefile.merlin
Add indexer tool (WIP)
Completion: use deepest_before
Travis: use only 4.02
Travis: remove minor compiler versions
Emacs: rework error display infrastructure
New indexer runs inside merlin and doesn't require a db