update link travis to README and fixed opensdk link

.travis.yml

@@ -3,7 +3,7 @@ before_install:
 - sudo apt-get -qq update
 - sudo apt-get install -y python-serial srecord
 install:
-- wget https://github.com/nodemcu/nodemcu-firmware/raw/master/tools/esp-open-sdk.tar.gz
+- wget https://github.com/nodemcu/nodemcu-firmware/raw/master/tools/esp-open-sdk.tar.gz -O tools/esp-open-sdk.tar.gz
 - tar -zxvf tools/esp-open-sdk.tar.gz
 - export PATH=$PATH:$PWD/esp-open-sdk/sdk:$PWD/esp-open-sdk/xtensa-lx106-elf/bin
 - wget http://bbs.espressif.com/download/file.php?id=1613 -O tools/ESP8266_NONOS_SDK_V2.0.0_16_07_19.zip

README.md

@@ -1,6 +1,6 @@
 **esp_mqtt**
 ==========
-![](https://travis-ci.org/tuanpmt/esp_mqtt.svg?branch=master)
+[![](https://travis-ci.org/tuanpmt/esp_mqtt.svg?branch=master)](https://travis-ci.org/tuanpmt/esp_mqtt)
 
 This is MQTT client library for ESP8266, port from: [MQTT client library for Contiki](https://github.com/esar/contiki-mqtt) (thanks)