Update elasticsearch-php to 5.4

[jdreesen]

Updates elasticsearch/elasticsearch to the latest v5 version.

Changelog: https://github.com/elastic/elasticsearch-php/blob/5.0/CHANGELOG.md#release-540
Changes: elastic/elasticsearch-php@v5.3.2...v5.4.0

[p365labs]

@jdreesen can u update the changelog?
I was wondering if we can update also the README version matrix as it is master branch

Elastica	ElasticSearch	elasticsearch-php	PHP

[jdreesen]

The build failure on PHP 5.6 is unrelated.

[p365labs]

yes but why is failing?

[jdreesen]

Somehow xdebug could not be installed when building the docker container.

Step 6/15 : RUN pecl install xdebug-2.3.2

 ---> Running in 73c0cd3425c1

No releases available for package "pecl.php.net/xdebug"

install failed

The command '/bin/sh -c pecl install xdebug-2.3.2' returned a non-zero code: 1

It seems to work in #1647 though:

Step 6/15 : RUN pecl install xdebug-2.3.2

 ---> Running in cd63d433dd96

downloading xdebug-2.3.2.tgz ...

Starting to download xdebug-2.3.2.tgz (266,287 bytes)

.............................................done

I'll try to re-trigger the build.

[jdreesen]

Seems it was just a hiccup on travis.

[p365labs]

thank u @jdreesen!