Added travis configuration

.travis.yml

+language: python
+python:
+    - "2.7"
+
+# Cache PlatformIO packages using Travis CI container-based infrastructure
+sudo: false
+cache:
+    directories:
+        - "~/.platformio"
+
+env:
+    - PLATFORMIO_CI_SRC=examples/SSD1306UiDemo/SSD1306UiDemo.ino
+    - PLATFORMIO_CI_SRC=examples/SSD1306SimpleDemo/SSD1306SimpleDemo.ino
+
+install:
+    - pip install -U platformio
+
+script:
+    - platformio ci --lib="." --board=nodemcuv2