title: plotly installation with R
body: <p>i want to install plotly package in R, from github</p>
  
  <pre><code>library(devtools)
  install_github("ropensci/plotly")
  </code></pre>
  
  <p>and i have an error message:</p>
  
  <pre><code>Downloading github repo ropensci/plotly@master
  Error in function (type, msg, asError = TRUE)  : couldn't connect to host
  </code></pre>
  
  <p>i have searched on the internet and i found that it's a problem of proxy, i tried:</p>
  
  <pre><code>set_config(
  use_proxy(url="https://github.com/ropensci/plotly", port=8080, username="***",password="***")
  )
  </code></pre>
  
  <p>but still have the same problem, i don't know what to put in url and port values, i have two accounts on Githup and plotly</p>
  
  <p>thank you for your help</p>