Update to Gradle 2.0

http://www.gradle.org/docs/current/release-notes
Use mongodb.org server to pull down packages

As a side effect, the installed version is now the latest
(which is 2.6.3 as of this commit) and this commit therefore
fixes https://github.com/travis-ci/travis-ci/issues/2246.
Install 5.5.9

On Trusty (14.04 LTS), the default version provided is 5.5.9,
and some users prefer to stick with that version.
Merge pull request #352 from travis-ci/ha-feature-php_5_5_9

Install PHP 5.5.9
Update change logs [skip ci]
Update Android SDK to 23.0.2

Fixes https://github.com/travis-ci/travis-ci/issues/2596
Retain only PHP runtime

To tighten feedback loop while we investigate
https://github.com/travis-ci/travis-ci/issues/2574
Revert "Retain only PHP runtime"

This reverts commit fb80a82308e6ceb7a123982ade226c093f331f7b.

Wrong branch. Sorry.
Add libicu-dev package

Fixes https://github.com/travis-ci/travis-ci/issues/2544
Put back 3.4.0

This was requested by a customer.
Please do not remove this unless it is cleared from the customer.
Leiningen 2.4.3

This version will use HTTPS when fetching stuff from Maven Central => big deal.
Merge pull request #355 from michaelklishin/patch-4

Leiningen 2.4.3
Add default .gitconfig with empty core.pager

When user calls git command that may invoke pager, it may hang
the build if input is expected.

Fixes https://github.com/travis-ci/travis-ci/issues/2651
Merge branch 'master' of github.com:travis-ci/travis-cookbooks
Add a newline to the end of file.

This makes appending new options cleaner.
Merge pull request #356 from whatthejeff/patch-1

Add a newline to the end of file.
Updating `nvm` to v0.13.1.

This includes a zsh fix, as well as the `nvm exec` command.
Merge pull request #357 from ljharb/update_to_nvm_0_13_1

Updating `nvm` to v0.13.1
Update Firefox to 31.0esr
Update change log [skip ci]