Minor fixes to the string_factor docs.

docs/specifications/string_factor.Rmd

@@ -12,7 +12,7 @@ cat("# String factor (", as.character(.version), ")", sep="")
 ## Overview
 
 The `string_factor` format provides an on-disk representation of a factor (i.e., enumerated type).
-This is based on R's factor.
+This is based on R's base factor type.
 
 ## Metadata
 
@@ -26,7 +26,7 @@ cat("  This should be set to \"", as.character(.version), "\".", sep="")
 ### Files
 
 The directory should contain the `contents.h5` HDF5 file.
-This should contain a `sting_factor` group, which should in turn contain `levels`.
+This should contain a `string_factor` group, which should in turn contain `levels`.
 This is a 1-dimensional string dataset containing the factor levels.
 The datatype should be representable by a UTF-8 encoded string.
 All levels should be unique.