Fix broken links and empty cell (#415)

* Update quick-start.jmd

* Update performancetips.jmd

Author: yebai

tutorials/docs-13-using-turing-performance-tips/performancetips.jmd

@@ -164,7 +164,3 @@ Then define the `Turing` model using the new functions as such:
     return x .~ Normal(c, d)
 end
 ```
-
-```julia
-
-```

tutorials/docs-14-using-turing-quick-start/quick-start.jmd

@@ -1,14 +1,14 @@
 ---
 title: Quickstart
-permalink: /docs/using-turing/quickstart
+permalink: /docs/using-turing/quick-start
 redirect_from: docs/1-quickstart/
 weave_options:
   error : false
 ---
 
 # Probabilistic Programming in Thirty Seconds
 
-If you are already well-versed in probabilistic programming and just want to take a quick look at how Turing's syntax works or otherwise just want a model to start with, we have provided a complete Bayesian coin-flipping model below.
+If you are already well-versed in probabilistic programming and want to take a quick look at how Turing's syntax works or otherwise just want a model to start with, we have provided a complete Bayesian coin-flipping model below.
 
 This example can be run wherever you have Julia installed (see [Getting Started](%7B%7Bsite.baseurl%7D%7D/docs/using-turing/get-started)), but you will need to install the packages `Turing` and `StatsPlots` if you have not done so already.