Update CHANGELOG for v11.11.0-rc1

CHANGELOG.md

+v11.11.0-rc1 (2019-04-05)
+
+- Fix git lfs not getting submodule objects !1298
+- Add homebrew installation method for macOS runners !837
+- mention the 59th second timeperiod issue in the docs !490
+- Refactor macOS install instructions !1303
+- Edit note on edge case !1304
+- Extract unsupportedOSTypeError to errors pkg !1305
+- Optimise trace handling for big traces !1292
+- Cleanup feature flags mess !1312
+- Add more documentation for node tolerations !1318
+- Typo: varialbes -> variables !1316
+- Allow to configure FF using config.toml !1321
+- Update link to the introduction of custom build directories !1302
+- Allow to use FF to configure `/builds` folder !1319
+- Create a single source of truth for feature flags !1313
+- Clear up docs on how to select shell !1209
+- Update feature flag documentation !1326
+- Refactor Helper Image package to work with Kubernetes !1306
+- Fix broken internal links !1332
+- Refactor helperimage package tests !1327
+- Change deprecation of FF_USE_LEGACY_BUILDS_DIR_FOR_DOCKER to 12.3 !1330
+- Update cmd script example !1333
+- Better explain the workflow in Docker executors doc !1310
+- Exclude mock files from coverage reporting !1334
+- Fix link syntax in advanced-configuration.md !1311
+- Docs: Update contributing links from gitlab-ce !1308
+- Update docker executor Executor Options initialization !1296
+- Add test case for Linux helper image !1335
+- Extract volumes configuration to a separate struct !1261
+
 v11.10.0 (2019-04-22)
 
 **Deprecations:**