Updated the minimum php version requirement to v7.3 (required by vend…

…or packages that also support v8.0) (alextselegidis#993).

composer.json

@@ -32,7 +32,7 @@
         }
     },
     "require": {
-        "php": ">=7.0",
+        "php": ">=7.3",
         "ext-curl": "*",
         "ext-json": "*",
         "ext-mbstring": "*",

docs/installation-guide.md

@@ -8,7 +8,7 @@ Easy!Appointments is a web appointment scheduler that can be installed and run i
 ### Installation
 There are 6 steps you must follow during the installation process.
 
-  1. **Make sure that your server has at least the following applications/tools installed: Apache(v2.4), PHP(v7.0) and MySQL(v5.7).** Easy!Appointments needs these programs to run. Most of the web hosting companies provide these tools within their Linux hosting plans. If you want to install Easy!Appointments on your local server use one of the pre-made bundles available on the web (XAMPP, MAMP, WAMP ...), all of which are free to use. If you plan to use the Google Calendar synchronization you will need the **php_curl** extension installed and enabled as well.
+  1. **Make sure that your server has at least the following applications/tools installed: Apache(v2.4), PHP(v7.3) and MySQL(v5.7).** Easy!Appointments needs these programs to run. Most of the web hosting companies provide these tools within their Linux hosting plans. If you want to install Easy!Appointments on your local server use one of the pre-made bundles available on the web (XAMPP, MAMP, WAMP ...), all of which are free to use. If you plan to use the Google Calendar synchronization you will need the **php_curl** extension installed and enabled as well.
   2. **Create a new database (or use an existing one).** The database is necessary for storing the system data. Therefore your hosting plan must include at least one MySQL database. You must also get the database administration credentials because they will be needed later on.
   3. **Upload the Easy!Appointments source files to your server.** You can place the files into a directory with named "easyappointments" or "appointments" or "book" etc. Make sure that you mark the Easy!Appointments folder URL because it will be needed in the following step. For example if the system files are placed in the this directory ".../httpdocs/easyappointments/" then the URL to this folder will be "http://your-domain.com/easyappointments". This URL will be needed in the following steps.
   4. **Ensure that the "storage" directory is writable.** Session information, logs and any other kind of files will land into the "storage" directory so make sure that it has the correct permissions and that is writable.