Install ExtUtils::MakeMaker with CPANM

This updates ExtUtils::MakeMaker to the latest version.

Fixes https://github.com/travis-ci/travis-ci/issues/2740
Add Perl runtime that has -Duseithreads

This will coexist with -Duseshrplib, and will be named -extras.

For backward compatibility, `5.*-shrplib` aliases are also created.

This fixes https://github.com/travis-ci/travis-ci/issues/2709
Update changelog
Update `nvm` to v0.15.0.

Fixes `nvm copy-packages`; adds `$NVM_SYMLINK_CURRENT` env var to
prevent creation of a "current" symlink; makes `sha1sum` have a higher
priority than `shasum`.
Merge pull request #372 from ljharb/update_to_nvm_0_15_0

Update `nvm` to v0.15.0
Invoke perlbrew-installer with bash

The shebang line is incorrectly set to invoke sh.

See https://github.com/gugod/App-perlbrew/issues/407
Merge branch 'master' of github.com:travis-ci/travis-cookbooks
Merge branch 'ha-feature-perl-extra'
Mark 2014/09/05 rollout
Revert "Invoke perlbrew-installer with bash"

This reverts commit dcf629c3a43d84d815d36c71ed06d11f6faa71ed.

https://github.com/gugod/App-perlbrew/issues/407 has been fixed.
Prevent CouchDB from starting on boot
Merge pull request #373 from travis-ci/ha-test-disable-couchdb-on-boot

Prevent CouchDB from starting on boot
Updating nvm to v0.16.0
Merge pull request #374 from ljharb/update_to_nvm_0_16_0

Updating nvm to v0.16.0
Update to nvm v0.16.1
Merge pull request #375 from ljharb/update_to_nvm_0_16_1

Update to nvm v0.16.1
Support erlang 17.2 and 17.3 with kerl
Leiningen 2.5.0
Merge pull request #377 from michaelklishin/patch-4

Leiningen 2.5.0
add ssh.github.com known_hosts