Filter folders in "man"

Roxygen will try to access folders as if they were ".Rd" files in the "man" directory (at least in Windows).

See the following thread for more details:
https://groups.google.com/forum/#!topic/rdevtools/QIsmPk_YL_U
Filter folders in "man" (this time is right)

Add a negation to the line I previously wrote...
Fix suggested by eibanez on May 14.
Filter folders in "man" in two more places, as suggested by eibanez.
Fix regex buglet.
Merge branch 'master' of github.com:klutometis/roxygen
Merge pull request #248 from eibanez/patch-1

Filter folders in "man"
Merge pull request #274 from tobiaskley/master

Addition to ' Filter folders in "man" ', as suggested by eibanez on May 14.
Don't modify collate if not @include.

Closes #302. Closes #303.
Merge branch 'master' of github.com:klutometis/roxygen
Tests for update_collate contributed by @Geoff99.

Closes #304
Add vignette improvements from @tbates.

Closes #308
Note about stringr
Update news
Bump version
Update version in generated docs
Add revdep checks
Move function def above usage