Add support for PHP 7.2

Author: xiehan

.travis.yml

@@ -4,6 +4,7 @@ php:
 - '5.6'
 - '7.0'
 - '7.1'
+- '7.2'
 - hhvm
 notifications:
   email: false

CONTRIBUTING.md

@@ -68,7 +68,7 @@ This project includes tests which can be executed with PHPUnit.
 
 - `./vendor/bin/phpunit`: runs all unit tests
 
-PHPUnit is configured to generate coverage reports in a `coverage` folder under `test-results` in the root of the project. Overall test coverage can viewed by opening `test-results/coverage/index.html`. (N.B. These coverage reports are purposely excluded from source control.) Note that [Xdebug must be enabled](https://xdebug.org/docs/install) in order for code coverage to be generated.
+PHPUnit is configured to generate coverage reports in a `coverage` folder under `test-results` in the root of the project. (N.B. These coverage reports are purposely excluded from source control.) Note that [Xdebug must be enabled](https://xdebug.org/docs/install) in order for code coverage to be generated.
 
 XML files are also generated for reporting test results and coverage on a CI server; again, those can be found under `test-results`.
 

phpunit.xml

@@ -23,7 +23,6 @@
         </whitelist>
     </filter>
     <logging>
-        <log type="coverage-html" target="test-results/coverage" lowUpperBound="35" highLowerBound="70"/>
         <log type="coverage-clover" target="test-results/coverage.xml"/>
         <log type="junit" target="test-results/junit.xml" logIncompleteSkipped="false"/>
     </logging>