The driver for the ESP8266 WiFi module - isConnected function added, working and tested with mbed os 5.7.6

Fork of esp8266-driver by ESP8266

Revision:
0:6946b0b9e323
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ESP8266/ATParser.lib	Thu Jan 12 21:57:48 2017 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/ATParser/#269f14532b98442669c50383782cbce1c67aced5