Support API Elements Parse Result

Update dependencies to support the Refract Parse Result instead of the AST
Parse Result. Deprecated API Blueprint AST support has been removed in
drafter 4.0.

https://github.com/apiaryio/drafter/blob/master/CHANGELOG.md#breaking-1

- Update drafter (NPM) to 2.0.0-pre.1

  https://github.com/apiaryio/drafter-npm/releases/tag/v2.0.0-pre.1

- Fix build on Mac 10.13.6

  See apiaryio/protagonist#191 for details

- Replace my own aglio-theme-olio

  https://github.com/Gasol/aglio-theme-olio/tree/lib

- Update gitignore to ignore cache directory and yarn related files

.gitignore

@@ -1,8 +1,11 @@
 .idea
+/cache
 node_modules
 npm-debug.log
 lib
 test-js
 coverage.html
 example.html
 example-compiled.apib
+yarn-error.log
+yarn.lock