travish.sh: delete superfluous echo commands

Travis output prints the script’s commands, so the echo commands were
repetitive. Not sure what `echo “yes”` in line 13 accomplished.
travis.sh: remove redundant pinning of flow

We should rely on the default URL specified in biorepo, which already
provides the same URL that was being pinned to.
travis.sh: move eval command to correct place

It should be done immediately after `opam init`.
OMakeroot: delete `run_tests` command

As biocaml_tests is expanded, we’ll likely have sub-commands like as
biocaml_benchmarks does. Thus, having a single omake target won’t
scale. Just need to call the executable directly.
travis.sh: fix dependency on `future`

Commit b9c66e181b3354a99bb7f57c06ad5fa4713844e9 mistakenly did this
wrong: `flow` was added again instead of `future`. Also, be explicit
about depending on the master branch of `future`.
travis.sh: install aspcud

This is the recommended solver for OPAM, which will use it by default
if available.