documented preserve_order in Geom.line
wording tweak
wording tweak
remove duplicated misplaced argument description
geom_subplot_grid.md: typo.
Merge pull request #236 from dchudz/geom-line-document-preserve-order

documented preserve_order in Geom.line
Merge pull request #237 from mschauer/patch-1

geom_subplot_grid.md: typo.
src and docs for Geom.path
doc clarification
Merge pull request #238 from dchudz/add-path-geom

adds Geom.path, with documentation