Update Travis CI configuration - updated legacy deps

Added ocramius/proxy-manager to legacy deps.

Author: michalbundyra

.travis.yml

@@ -19,7 +19,7 @@ matrix:
     - php: 5.6
       env:
         - DEPS=locked
-        - LEGACY_DEPS="phpunit/phpunit"
+        - LEGACY_DEPS="ocramius/proxy-manager phpunit/phpunit"
     - php: 5.6
       env:
         - DEPS=latest
@@ -29,7 +29,7 @@ matrix:
     - php: 7
       env:
         - DEPS=locked
-        - LEGACY_DEPS="phpunit/phpunit"
+        - LEGACY_DEPS="ocramius/proxy-manager phpunit/phpunit"
     - php: 7
       env:
         - DEPS=latest