Do not depend on camlp4o to build a project

The solution is quite hackish but I haven't find a better way yet ...
Compile and run the tests in Travis CI
Revert "Do not depend on camlp4o to build a project"

This reverts commit 5c83e46d163f26744c2546ec9104346a495d9ff2.
Fix the opam file
Do not use camlp4o when this is not necessary
Fix Travis to work with opam 1.1
Fix generation of META dependencies

Previously, only the library dependencies were taken into account, and not the individual compilation unit ones.
Do not generate an empty META file
Assemblage does not depend on camlp4 anymore

(and it does fancy linking tricks)
Fix linking args when building a binary with multiple files
Add a configure option to not depend on ocaml-dumast at all
Merge branch 'master' of github.com:samoht/assemblage into no-camlp4

Conflicts:
	bootstrap.sh
Remove warnings
Merge branch 'master' of github.com:samoht/assemblage into no-camlp4

Conflicts:
	bootstrap.sh
Clean-ups
Update Travis scripts to not depend on ocaml-dumpast
Fix bootstrap: optcomp is not required anymore
Make the tests pass

Warn the user when he needs to install ocaml-dumpast
Merge pull request #71 from samoht/no-camlp4

Do not depend on camlp4o to build a project