clean up vignette metadata

Author: mountainMath

vignettes/cansim.Rmd

@@ -1,7 +1,5 @@
 ---
 title: "Getting started with the cansim package"
-author: ""
-date: "`r Sys.Date()`"
 output: rmarkdown::html_vignette
 vignette: >
   %\VignetteIndexEntry{Getting started with the cansim package}

vignettes/listing_cansim_tables.Rmd

@@ -1,9 +1,5 @@
 ---
 title: "Listing Statistics Canada data tables"
-description: >
-  An example of how to identify and search for available datasets using the cansim package.
-author: ""
-date: "`r Sys.Date()`"
 output: rmarkdown::html_vignette
 vignette: >
   %\VignetteIndexEntry{Listing Statistics Canada data tables}

vignettes/retrieving_cansim_vectors.Rmd

@@ -1,9 +1,5 @@
 ---
 title: "Retrieving individual Statistics Canada vectors"
-description: >
-  A worked example showing how to retrieve individual data vectors instead of entire tables. 
-author: ""
-date: "`r Sys.Date()`"
 output: rmarkdown::html_vignette
 vignette: >
   %\VignetteIndexEntry{Retrieving individual Statistics Canada vectors}

vignettes/working_with_hierarchies.Rmd

@@ -1,9 +1,5 @@
 ---
 title: "Working with Statistics Canada data table object hierarchies"
-description: >
-  Data retrieved from Statistics Canada frequently has complicated hierarchical structures. The cansim provides convenience tools to make it easier to work with these structures. 
-author: ""
-date: "`r Sys.Date()`"
 output: rmarkdown::html_vignette
 vignette: >
   %\VignetteIndexEntry{Working with Statistics Canada data table object hierarchies}