Use yarn --frozen-lockfile on Travis CI build

The behavior causing the Travis CI builds is a bug, see
yarnpkg/yarn#1568

A more in-depth conversation around the lockfile behavior is in this
issue: yarnpkg/yarn#570

Run `yarn upgrade to update yarn.lock.

.atomist/build/travis-build.bash

@@ -61,7 +61,7 @@ function main () {
 
     if [[ -f .atomist/package.json ]]; then
         msg "running yarn"
-        if ! ( cd .atomist && yarn ); then
+        if ! ( cd .atomist && yarn --frozen-lockfile ); then
             err "yarn failed"
             return 1
         fi
@@ -131,6 +131,7 @@ function main () {
         msg "publishing archive to $TEAM_ID"
         if ! $rug publish -a "$project_version"; then
             err "failed to publish archive $project_version"
+            git diff
             return 1
         fi
 

.atomist/yarn.lock

@@ -1508,9 +1508,13 @@ traverse@^0.6.6:
   version "0.6.6"
   resolved "https://registry.yarnpkg.com/traverse/-/traverse-0.6.6.tgz#cbdf560fd7b9af632502fed40f918c157ea97137"
 
+tslib@^1.6.0:
+  version "1.6.1"
+  resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.6.1.tgz#b77b09abc5fa4935e157d838b80e36dad47152c4"
+
 tslint@^5.0.0:
-  version "5.1.0"
-  resolved "https://registry.yarnpkg.com/tslint/-/tslint-5.1.0.tgz#51a47baeeb58956fcd617bd2cf00e2ef0eea2ed9"
+  version "5.2.0"
+  resolved "https://registry.yarnpkg.com/tslint/-/tslint-5.2.0.tgz#16a2addf20cb748385f544e9a0edab086bc34114"
   dependencies:
     babel-code-frame "^6.22.0"
     colors "^1.1.2"
@@ -1520,9 +1524,10 @@ tslint@^5.0.0:
     optimist "~0.6.0"
     resolve "^1.3.2"
     semver "^5.3.0"
-    tsutils "^1.4.0"
+    tslib "^1.6.0"
+    tsutils "^1.8.0"
 
-tsutils@^1.4.0:
+tsutils@^1.8.0:
   version "1.8.0"
   resolved "https://registry.yarnpkg.com/tsutils/-/tsutils-1.8.0.tgz#bf8118ed8e80cd5c9fc7d75728c7963d44ed2f52"