Added fastlane configuration files

[fastlane](https://fastlane.tools) is an established Continuous Delivery solution for iOS/Mac projects. The configuration files are similar to a `Podfile`, also Ruby based. 

Some examples:
- https://github.com/wikimedia/apps-ios-wikipedia/blob/master/fastlane/Fastfile
- https://github.com/wikimedia/apps-ios-wikipedia/blob/master/fastlane/Deliverfile
- https://github.com/artsy/eidolon/blob/master/fastlane/Fastfile
- https://github.com/fastlane/examples/blob/master/MindNode/Fastfile

The configuration files added with this pull request: `Fastfile`, `Deliverfile` and `Snapfile` 👍

lib/linguist/languages.yml

@@ -2833,6 +2833,8 @@ Ruby:
   - Appraisals
   - Berksfile
   - Buildfile
+  - Deliverfile
+  - Fastfile
   - Gemfile
   - Gemfile.lock
   - Guardfile
@@ -2840,6 +2842,7 @@ Ruby:
   - Mavenfile
   - Podfile
   - Puppetfile
+  - Snapfile
   - Thorfile
   - Vagrantfile
   - buildfile