template with extension .r are supported on case-sensitive file systems

- add tests to cover existing and failing behavior
Merge pull request #135 from krlmlr/115-lcase-r-ext

Supported templates with extension .r on case-sensitive file systems
Add version number to news
Update NEWS about S4 changes
Merge branch 'master' of github.com:klutometis/roxygen
Add explicit object model.
For R object being documented
Create S3 objects when parsing
Tests for topic names
Simplify src ref parser registration
Refactoring parse.srcref
Add S3 tools from roxygen3
Capture S3 metadata when parsing srcs
Rewrite namespace roclet.
Favouring clarity over concision, and using new object class
Ensure all tests pass
Keep existing useDynLib behaviour
Test useDynLib doesn't quote when comma present.
Closes #124
Test and describe export for S3 methods
Use @export instead of @s3method.
Also add a few missing exports
Better tests for class topic name.
Use object name not old format
Rewrite usage to use new classes