Reformatted code and added support for all payment methods

This commit adds the following payment methods:
- EPS
- Giftcards
- Giropay
- ING Home'Pay
- KBC/CBC

I've also ran a reformatter to clean up the code and added composer
instead of git modules. The latter enables us to keep up-to-date
with the last Mollie library in a more modern manner.

composer.json

@@ -0,0 +1,8 @@
+{
+  "require": {
+    "mollie/mollie-api-php": "^2.0"
+  },
+  "config": {
+    "vendor-dir": "src/mollie/vendor"
+  }
+}