Verify sketches as part of travis build

Squashed commits:
[7d1b42f] Encrypt token, skip some tests
[17b8f39] Fix sha1 example path
[f3050b1] Fix build, add webhook
[fd2c9bd] Fix build errors, update mDNS library readme
[7b87031] Make common.sh more flexible
[3ba3eb2] Test all sketches
[87beb8a] Build all sketches in esp8266 core
[f2464f1] Fix paths
[823a9ae] Remove sudo usage
[7fce734] Fix arduino commands
[619bc7d] Move all commands into travis script
[15a5ada] First attempt test runner

tests/common.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+function build_sketches()
+{
+    local arduino=$1
+    local srcpath=$2
+    local sketches=$(find $srcpath -name *.ino)
+    for sketch in $sketches; do
+        local sketchdir=$(dirname $sketch)
+        if [[ -f "$sketchdir/.test.skip" ]]; then
+            echo -e "\n\n ------------ Skipping $sketch ------------ \n\n";
+            continue
+        fi
+        echo -e "\n\n ------------ Building $sketch ------------ \n\n";
+        $arduino --verify --verbose $sketch;
+        local result=$?
+        if [ $result -ne 0 ]; then
+            echo "Build failed ($1)"
+            return $result
+        fi
+    done
+}