Add a placeholder opal/rails for old bundler
Bump version
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Add `Rails.application.config.opal`

Accepts:
  - method_missing: `<Boolean>` (default: `true`)
  - optimized_operators: `<Boolean>` (default: `true`)
  - arity_check: `<Boolean>` (default: `false`)
  - const_missing: `<Boolean>` (default: `true`)
Update RSpec
Reset default_options before each example
Remove assets cache before each run of the spec suite
Add a warning about stale cached assets after changing opal version or config
Add gem version badge
Bump version
Add the source map generator

Based on magic comments from the elia/source-map branch on opal:
- /*file:path.js.rb*/ for files
- /*:34*/ for lines
Tell bundler where to get the source-maps enabled opal
Cleanup test_app routes
Serve source-maps from a controller
Add a basic spec for source-maps
Pathnames ain't strings
Provide the test_app with a root path
Use `rails new -j opal` in the test app
Add the pathname stub to the processor spec