added travis

.travis.yml

@@ -0,0 +1,29 @@
+language: c
+sudo: false
+
+cache:
+  directories:
+    - ~/arduino_ide
+    - ~/.arduino15/packages/
+
+git:
+  depth: false
+  quiet: true
+
+env:
+  global:
+    - ARDUINO_IDE_VERSION="1.8.7"
+    - PRETTYNAME="DHT sensor library"
+
+before_install:
+  - source <(curl -SLs https://raw.githubusercontent.com/adafruit/travis-ci-arduino/master/install.sh)
+
+install:
+  - arduino --install-library "Adafruit Unified Sensor"
+
+script:
+  - build_main_platforms
+
+after_success:
+  - source <(curl -SLs https://raw.githubusercontent.com/adafruit/travis-ci-arduino/master/library_check.sh)
+  - source <(curl -SLs https://raw.githubusercontent.com/adafruit/travis-ci-arduino/master/doxy_gen_and_deploy.sh)