build: capture code coverage stats during Travis-CI run

The results are uploaded to codecov.io to create readable reports.

.travis.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+set -e
+echo "" > coverage.txt
+
+for d in $(go list ./... | grep -v vendor); do
+    go test -coverprofile=profile.out -covermode=atomic $d
+    if [ -f profile.out ]; then
+        cat profile.out >> coverage.txt
+        rm profile.out
+    fi
+done

.travis.yml

@@ -4,3 +4,12 @@ go:
   - 1.7.x
   - 1.8.x
   - tip
+
+before_install:
+  - go get -t -v ./...
+
+script:
+  - ./.travis.sh
+
+after_success:
+  - bash <(curl -s https://codecov.io/bash)