Support PHP 7.3 (laradock#2028)

* Support PHP 7.3
* travics-ci build test by pass:
  * SSH2 extension does not yet support PHP 7.3
  * V8JS extension does not yet support PHP 7.3.
  * xdebug extension does not yet support PHP 7.3.
  * memcached extension does not yet support PHP 7.3.

Author: bestlong

.travis.yml

@@ -11,18 +11,21 @@ env:
     - PHP_VERSION=7.0 BUILD_SERVICE=workspace
     - PHP_VERSION=7.1 BUILD_SERVICE=workspace
     - PHP_VERSION=7.2 BUILD_SERVICE=workspace
+    - PHP_VERSION=7.3 BUILD_SERVICE=workspace
 
     - PHP_VERSION=5.6 BUILD_SERVICE=php-fpm
     - PHP_VERSION=7.0 BUILD_SERVICE=php-fpm
     - PHP_VERSION=7.1 BUILD_SERVICE=php-fpm
     - PHP_VERSION=7.2 BUILD_SERVICE=php-fpm
+    - PHP_VERSION=7.3 BUILD_SERVICE=php-fpm
 
     - PHP_VERSION=hhvm BUILD_SERVICE=hhvm
 
     # - PHP_VERSION=5.6 BUILD_SERVICE=php-worker
     - PHP_VERSION=7.0 BUILD_SERVICE=php-worker
     - PHP_VERSION=7.1 BUILD_SERVICE=php-worker
     - PHP_VERSION=7.2 BUILD_SERVICE=php-worker
+    - PHP_VERSION=7.3 BUILD_SERVICE=php-worker
 
     - PHP_VERSION=NA BUILD_SERVICE=solr
     - PHP_VERSION=NA BUILD_SERVICE="mssql rethinkdb aerospike"

DOCUMENTATION/content/introduction/index.md

@@ -58,7 +58,7 @@ That's it! enjoy :)
 <a name="features"></a>
 ## Features
 
-- Easy switch between PHP versions: 7.2, 7.1, 5.6...
+- Easy switch between PHP versions: 7.3, 7.2, 7.1, 5.6...
 - Choose your favorite database engine: MySQL, Postgres, MariaDB...
 - Run your own combination of software: Memcached, HHVM, Beanstalkd...
 - Every software runs on a separate container: PHP-FPM, NGINX, PHP-CLI...

env-example

@@ -37,7 +37,7 @@ COMPOSE_PROJECT_NAME=laradock
 
 ### PHP Version ###########################################
 
-# Select a PHP version of the Workspace and PHP-FPM containers (Does not apply to HHVM). Accepted values: 7.2 - 7.1 - 7.0 - 5.6
+# Select a PHP version of the Workspace and PHP-FPM containers (Does not apply to HHVM). Accepted values: 7.3 - 7.2 - 7.1 - 7.0 - 5.6
 PHP_VERSION=7.2
 
 ### Phalcon Version ###########################################