updating katlongo's repo

Hi @katlongo,

You don't need to set this variable if you simply assume that for any script in ohiprep you're current working directory is '~/Documents/K_Longo/GitHub/ohiprep-katlongo'. In fact, it might mess up scripts when run on our machines.

I recommend moving your ohiprep repository to something simpler '~/github/ohiprep'. Then if you need to get to another repository, like ohi-global or ohicore, you can simply back up a directory '../ohi-global/etc'. Conversely, scripts from those repositories could do the same. For instance, check out [ohi-global:calculate_scores_all.R](https://github.com/OHI-Science/ohi-global/blob/master/calculate_scores_all.R#L10-L11) which sets `dirs$ohiprep       = '../ohiprep'` for swapping out the `ohiprep:` prefix in the dir_* fields from [layers_global](https://docs.google.com/a/nceas.ucsb.edu/spreadsheet/ccc?key=0At9FvPajGTwJdEJBeXlFU2ladkR6RHNvbldKQjhiRlE&usp=drive_web#gid=0). Make sense?