remove file.copy instruction in compile_dll

the command was silently failing, but apparently not posing any problem, so I just removed it
Upgrade roxygen2
Create draft vignette with use_vignette.
Closes #572
Re-add knitr dep. Install rmarkdown
Don't build_vignettes by default when installing packages.
Closes #573
Improved missing_s3
Export all S3 methods
Update tests
Bump version to 1.5.0.9001
Devtools needs to be loaded for windows.
Fix partial match note
Fix generic arg mismatch
Fix another partial arg warning
remote_download.url_remote: if ext contains '.tar.gz', preseve '.tar'. Fixes #580
install_remote: remove MD5 for DESCRIPTION. Fixes #582
Remove extraneous browser()
Merge pull request #568 from adrtod/patch-4

remove file.copy instruction in compile_dll
Fix typo. Closes #578
Organise news
More news tidying