[abacus] Pruning our build matrix for faster Travis-CI builds

Jean-Sebastien Delfino

I've been seeing slower Travis-CI builds recently so I've pruned our build
matrix a bit in an attempt to speed things up.

Here are the combinations left in our Travis build matrix, down from 8 to 4:
- os: "linux"
env: NODE_VERSION="4.0"
- os: "linux"
env: NODE_VERSION="0.12"
- os: "linux"
env: NODE_VERSION="0.10"
- os: "osx"
env: NODE_VERSION="4.0"

I've removed the iojs version from the build matrix as io.js has now
converged with node.js 4.0, and I'm also only building with node.js 4.0 on

The OS X build is a bit slower than the Linux builds but I thought it'd be
important to keep at least one OS X build as most of us develop on OS X and
some of the logs we've seen in Github issues from our users show OS X as

If the matrix is now missing a combination you really care about, please
post here and I'll be happy to add it back ...

-- Jean-Sebastien

Join {cf-dev@lists.cloudfoundry.org to automatically receive all group messages.