Update travis to install ext-fiber

.travis.yml

@@ -8,11 +8,6 @@ addons:
       - libevent-dev
 
 php:
-  - 7.0
-  - 7.1
-  - 7.2
-  - 7.3
-  - 7.4
   - nightly
 
 matrix:
@@ -27,6 +22,7 @@ before_install:
   - php travis/change-composer.php drop-config
 
 install:
+  - travis/install-fiber.sh
   - travis/install-uv.sh
   - travis/install-ev.sh
   - travis/install-event.sh

travis/install-fiber.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+git clone https://github.com/amphp/ext-fiber \
+ && pushd ext-fiber \
+ && phpize \
+ && ./configure \
+ && make -j4 \
+ && make install \
+ && popd \
+ && echo "extension=fiber.so" >> "$(php -r 'echo php_ini_loaded_file();')";