edited highbrow and highplos fxns
added function facetplos
fixed output for plosword, closes #50
removed highlighting options from searchplos, no more plos class
removed highlighting params etc from search fxns
now pushing vignette to vignettes dir and new makefile workflow
updated date and bumped version no in desc file, closes #55, closes #56
fixed tests
updated docs for facet and highlight fxns