Use phar version of ocular

It's impossible to install the latest version of Guzzle due
ocular (used to upload code coverage) depending on guzzlehttp/guzzle ~3.0.

See https://github.com/scrutinizer-ci/ocular/blob/master/composer.json

Closes #95

Inspired by https://github.com/Ocramius/ProxyManager/blob/master/.travis.coverage.sh

.travis.coverage.sh

@@ -0,0 +1,5 @@
+set -x
+if [[ "$TRAVIS_PHP_VERSION" != 'hhvm' && "$TRAVIS_PHP_VERSION" != '7.0' ]] ; then
+    wget https://scrutinizer-ci.com/ocular.phar
+    php ocular.phar code-coverage:upload --format=php-clover coverage.clover
+fi

.travis.yml

@@ -29,4 +29,4 @@ script:
   - vendor/bin/phpunit --coverage-text --coverage-clover=coverage.clover
 
 after_script:
-  - if [[ $TRAVIS_PHP_VERSION != 'hhvm' && $TRAVIS_PHP_VERSION != '7.0' ]]; then php vendor/bin/ocular code-coverage:upload --format=php-clover coverage.clover; fi
+  - sh .travis.coverage.sh

composer.json

@@ -21,7 +21,6 @@
     },
     "require-dev": {
         "phpunit/phpunit" : "~4.0||~5.0",
-        "scrutinizer/ocular": "~1.1",
         "squizlabs/php_codesniffer": "^2.3"
     },
     "autoload": {