[Rd] Running examples with R5 constructor from package failing

[Imanuel Costigan]

I am having an issue with reference classes (R5) in a package I am developing. They have both been illustrated in the `roxygentest` package I've got hosted on Github [1]. 

When I run `R CMD check .` on the source directory of my package I am told that:
> Error: could not find function "Blob"

However, when I install and load the package, I can successfully run the command in the example. 

Does someone know why this is happening?

The relevant definitions and the example (in Rd format):

R5 definition:
```
draw.Blob <- function (type = 'small') 
{
  'Something about blobs'
  type <<- 'small'
}

Blob <- setRefClass (
  Class = "Blob", 
  fields = list(type = 'character'),
  methods = list(draw = draw.Blob)
)
```

Example:
```
\examples{
Blob(type = 'small')
}
```

Cheers

[1] https://github.com/imanuelcostigan/roxygentest