A6 A7 gateway (GSM GPRS) (#195)

* init 2G gateway with SMS sending and receiving

* A6lib add

* add 2Ggateway call from setup and loop

* add schematic and image

lib/A6lib/library.json

@@ -0,0 +1,14 @@
+{
+    "name": "A6lib",
+    "keywords": [
+      "A6", "GSM", "mobile"
+    ],
+    "description": "An ESP8266/Arduino library for communicating with the A6 GSM module.",
+    "repository":
+    {
+        "type": "git",
+        "url": "https://github.com/skorokithakis/A6lib"
+    },
+    "frameworks": "arduino",
+    "platforms": "*"
+}