Use Yarn latest in e2e (#1534)

* Use Yarn latest in e2e

* Here too

* And here plz

Author: gaearon

tasks/e2e-installs.sh

@@ -68,7 +68,7 @@ npm install
 if [ "$USE_YARN" = "yes" ]
 then
   # Install Yarn so that the test can use it to install packages.
-  npm install -g yarn@0.17.10 # TODO: remove version when https://github.com/yarnpkg/yarn/issues/2142 is fixed.
+  npm install -g yarn
   yarn cache clean
 fi
 

tasks/e2e-kitchensink.sh

@@ -68,7 +68,7 @@ npm install
 if [ "$USE_YARN" = "yes" ]
 then
   # Install Yarn so that the test can use it to install packages.
-  npm install -g yarn@0.17.10 # TODO: remove version when https://github.com/yarnpkg/yarn/issues/2142 is fixed.
+  npm install -g yarn
   yarn cache clean
 fi
 

tasks/e2e-simple.sh

@@ -78,7 +78,7 @@ npm install
 if [ "$USE_YARN" = "yes" ]
 then
   # Install Yarn so that the test can use it to install packages.
-  npm install -g yarn@0.17.10 # TODO: remove version when https://github.com/yarnpkg/yarn/issues/2142 is fixed.
+  npm install -g yarn
   yarn cache clean
 fi