[danger] Update API usage

Dangerfile

@@ -1,13 +1,13 @@
 # Sometimes it's a README fix, or something like that - which isn't relevant for
 # including in a project's CHANGELOG for example
-declared_trivial = (pr_title + pr_body).include?("#trivial")
+declared_trivial = (github.pr_title + github.pr_body).include?("#trivial")
 
 # Make it more obvious that a PR is a work in progress and shouldn't be merged yet
-warn("PR is classed as Work in Progress") if pr_title.include? "[WIP]"
+warn("PR is classed as Work in Progress") if github.pr_title.include? "[WIP]"
 
 # Warn when there is a big PR
-warn("Big PR") if lines_of_code > 500
+warn("Big PR") if git.lines_of_code > 500
 
-if !modified_files.include?("CHANGELOG.md") && !declared_trivial
+if !git.modified_files.include?("CHANGELOG.md") && !declared_trivial
   fail("Please include a CHANGELOG entry. \nYou can find it at [CHANGELOG.md](https://github.com/orta/ARAnalytics/blob/master/CHANGELOG.md).")
-end
+end