Minor bugfix

Use seq_along(x) rather than 1:length(x).
Prefer seq_along(x) to 1:length(x)
Stop reimplementing pgpd
Prefer file.path to paste0

file.path is the recommended way to do path jiggling.
Merge pull request #6 from pdmetcalfe/bugfix/pgpd_duplicate

Reimplementing pgpd?
Merge pull request #7 from pdmetcalfe/bugfix/file.path

Prefer file.path to paste0
Merge pull request #5 from pdmetcalfe/bugfix/seq_along

More of a style preference than a bugfix...