Tweak various bits to get the tests running again (#66)

* Add a `behat.yml` so tests run as expected

* Bump `wp-cli/wp-cli-tests` to v3

* Bump platform requirements to PHP 5.6

* Behat dependency shouldn't be necessary

* Update `branch-alias`

Author: danielbachhuber

behat.yml

@@ -0,0 +1,7 @@
+default:
+  suites:
+    default:
+      contexts:
+        - WP_CLI\Tests\Context\FeatureContext
+      paths:
+        - features

composer.json

@@ -16,12 +16,11 @@
         "wp-cli/wp-cli": "^2"
     },
     "require-dev": {
-        "behat/behat": "~2.5",
-        "wp-cli/wp-cli-tests": "^2.1"
+        "wp-cli/wp-cli-tests": "^3.1"
     },
     "config": {
         "platform": {
-            "php": "5.4"
+            "php": "5.6"
         },
         "process-timeout": 7200,
         "sort-packages": true,
@@ -45,7 +44,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-main": "1.x-dev"
+            "dev-main": "2.x-dev"
         },
         "commands": [
             "find"