+Abella 2.0.2

Also removed abella.2.0.0, which is now obsolete
Abella 2.0.2 requires OCaml 4.01.0+
travis: Fix the check for package availability on older opams

turns out there used to be no good way of simply checking this, so I'm just trying to
install with --dry-run and expecting an empty stdout if the package is unavailable
vastly reduce the number of osx tests to reduce the worker backlog
Addition of portia, a literate programming tool.

Portia is a programmable text processor that allow to extract fragments from a
set of files and recompose some output files from them. It is meant to serve as
a literate programming preprocessor, agnostic to both the format used for the
documentation and the programming language, and thus is adapted to OCaml.

It is itself implemented using literate programming and needs funnelweb
(http://www.ross.net/funnelweb/) for bootstrap.
core 112.01.01
add ojs-base 0.2.0
cow.0.8.1: restrict to ocaml < 4.02 per mirage/ocaml-cow#48
added OCamltter 3.0.0
add stog 0.14.0
commit to enforce re-Travis
Merge branch 'master' of https://github.com/OCamlPro/opam-repository
fixed dependency
Remove unstable mirage-www package from the main repo
Merge pull request #2949 from samoht/mirage-www

Remove unstable mirage-www package from the main repo
travis: fix new opam with old compiler availability check
Merge pull request #2951 from dsheets/abella-and-travis

Fix the travis script for new opams with older compilers
If you skip, do it on a log.

but don't fall into the river.

of lava.
Merge pull request #2952 from dsheets/abella-and-travis

Travis: Skipping an install should print the reason for skipping
Merge pull request #2944 from dsheets/cow_0_8_1_ocaml_version

cow.0.8.1: restrict to ocaml < 4.02 per mirage/ocaml-cow#48