Build osx binary on travis and upload to bintray.

This requires a change to the make-branch script, to have it push the bump branch
to the docker remote instead of the user remote. Pushing to the docker remote
triggers the travis build, which builds the binary.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

script/travis/bintray.json.tmpl

@@ -1,7 +1,7 @@
 {
     "package": {
         "name": "${TRAVIS_OS_NAME}",
-        "repo": "master",
+        "repo": "${TRAVIS_BRANCH}",
         "subject": "docker-compose",
         "desc": "Automated build of master branch from travis ci.",
         "website_url": "https://github.com/docker/compose",
@@ -11,8 +11,8 @@
     },
 
     "version": {
-        "name": "master",
-        "desc": "Automated build of the master branch.",
+        "name": "${TRAVIS_BRANCH}",
+        "desc": "Automated build of the ${TRAVIS_BRANCH} branch.",
         "released": "${DATE}",
         "vcs_tag": "master"
     },