update tests to support php7.4, remove php7.1, and update doc for public properties

Author: noogen

.travis.yml

@@ -1,8 +1,8 @@
 language: php
 php:
-  - '7.1'
   - '7.2'
   - '7.3'
+  - '7.4'
 
 sudo: false
 

README.md

@@ -55,7 +55,7 @@ $classifier->fromJson($stateJson);
 
 Returns an instance of a Naive-Bayes Classifier.
 
-Pass in an optional `options` object to configure the instance. If you specify a `tokenizer` of `iTokenizer` instance in `options`, it will be used as the instance's tokenizer.
+Pass in an optional `options` object to configure the instance. If you specify a `tokenizer` function in `options`, it will be used as the instance's tokenizer.
 
 ### `$classifier->learn(text, category)`
 

composer.json

@@ -26,10 +26,10 @@
   }],
   "type": "library",
   "require": {
-    "php": ">=7.1"
+    "php": ">=7.2"
   },
   "require-dev": {
-    "phpunit/phpunit": "~6.3.0"
+    "phpunit/phpunit": "^8.0"
   },
   "autoload": {
     "psr-4": {