Add --hhvm-4.2-to-4.3 migration flag - <> => !=

Also only test on 4.2

.travis.yml

@@ -2,11 +2,7 @@ sudo: required
 language: generic
 services: docker
 env:
-  - HHVM_VERSION=latest
-  - HHVM_VERSION=nightly
-matrix:
-  allow_failures:
-    - env: HHVM_VERSION=latest
+  - HHVM_VERSION=4.2-latest
 install:
 - docker pull hhvm/hhvm:$HHVM_VERSION
 script:

src/__Private/MigrationCLI.hack

@@ -102,6 +102,13 @@ class MigrationCLI extends CLIWithRequiredArguments {
         'Apply all migrations for moving from 3.23 to 3.24',
         '--hhvm-3.23-to-3.24',
       ),
+      CLIOptions\flag(
+        () ==> {
+          $this->migrations[] = PHPLessThanGreaterThanOperatorMigration::class;
+        },
+        'Apply all migrations for moving from 4.2 to 4.3',
+        '--hhvm-4.2-to-4.3',
+      ),
       CLIOptions\flag(
         () ==> {
           $this->migrations[] = PHPLessThanGreaterThanOperatorMigration::class;