Renamed tests to .test.js & updated commands

refs: https://github.com/TryGhost/Team/issues/856
refs: https://github.com/TryGhost/Team/issues/756

- The .test.js extension is better than _spec.js as it's more obvious that it's an extension
- It also meaans we can use the --extension parameter in mocha, which should result in a better default behaviour for `yarn test`
- It also highlights that some of our tests were named incorrectly and were not (and still will not be) run (see https://github.com/TryGhost/Team/issues/856)
- Note: even with this change, `yarn test` is throwing errors, I believe because of this issue https://github.com/TryGhost/Team/issues/756

package.json

@@ -26,12 +26,12 @@
     "setup": "yarn install && knex-migrator init && grunt symlink && grunt init || (exit 0)",
     "main": "grunt shell:main && grunt subgrunt:init",
     "build": "grunt build",
-    "test": "mocha --require=test/utils/overrides.js --exit --trace-warnings --recursive --timeout=60000",
+    "test": "mocha --require=./test/utils/overrides.js --exit --trace-warnings --recursive --extension=test.js --timeout=60000",
     "test:all": "yarn test:unit && yarn test:acceptance && yarn test:regression",
     "test:debug": "DEBUG=ghost:test* yarn test",
-    "test:unit": "mocha --require=test/utils/overrides.js --exit --trace-warnings './test/unit/**/*_spec.js' --timeout=7000",
-    "test:acceptance": "mocha --require=test/utils/overrides.js --exit --trace-warnings './test/api-acceptance/**/*_spec.js' './test/frontend-acceptance/**/*_spec.js' --timeout=10000",
-    "test:regression": "mocha --require=test/utils/overrides.js --exit --trace-warnings  './test/regression/**/*_spec.js' --timeout=60000",
+    "test:unit": "mocha --require=./test/utils/overrides.js --exit --trace-warnings --recursive --extension=test.js './test/unit' --timeout=7000",
+    "test:acceptance": "mocha --require=./test/utils/overrides.js --exit --trace-warnings --recursive --extension=test.js './test/api-acceptance' './test/frontend-acceptance' --timeout=10000",
+    "test:regression": "mocha --require=./test/utils/overrides.js --exit --trace-warnings --recursive --extension=test.js  './test/regression' --timeout=60000",
     "test:slow": "yarn test:unit --reporter=mocha-slow-test-reporter && yarn test:acceptance --reporter=mocha-slow-test-reporter",
     "lint:server": "eslint --ignore-path .eslintignore 'core/server/**/*.js' 'core/*.js' '*.js'",
     "lint:shared": "eslint --ignore-path .eslintignore 'core/shared/**/*.js'",
@@ -73,7 +73,7 @@
     "@tryghost/logging": "0.1.3",
     "@tryghost/magic-link": "1.0.5",
     "@tryghost/members-api": "1.19.0",
-    "@tryghost/members-csv": "1.1.1",
+    "@tryghost/members-csv": "1.1.0",
     "@tryghost/members-ssr": "1.0.5",
     "@tryghost/mw-session-from-token": "0.1.22",
     "@tryghost/package-json": "1.0.2",