title: knitr::kable outputs code instead of a pretty table
body: <p>I recently updated to R 3.5.0 and RStudio 1.1.453 and now my kable function is not working properly.</p>
  
  <p>When I copy and paste the code and output, you see this: </p>
  
  <pre><code>library(knitr)
  fakedata&lt;-data.frame(Species = c(1:8), Sites = sample(1:25, 8, replace = TRUE), Positives = sample(1:100,8, replace=TRUE))
  kable(fakedata)
  
  
  | Species| Sites| Positives|
  |-------:|-----:|---------:|
  |       1|    22|        79|
  |       2|    25|        97|
  |       3|    19|        28|
  |       4|    15|        22|
  |       5|     9|        97|
  |       6|    14|        71|
  |       7|     1|        70|
  |       8|    21|        83|
  </code></pre>
  
  <p>I get no error at all, and the output is the same with or without Rmarkdown. 
  I also reinstalled MiKTeX.</p>
  
  <p>When I knit it to a document the output is simply blank, again with no errors.</p>
  
  <p>Is anyone else having this problem?
  Is there another update I am missing?</p>
  
  <p>Thanks</p>