title: readLines() does not read from HTTPS URL when called from system("rscript")
body: <p>When I directly call the following in RStudio, it works fine.</p>
  
  <pre><code>readLines("https://raw.githubusercontent.com/renkun-ken/rlist-tutorial/master/data/sample.yaml")
  </code></pre>
  
  <p>However, when I call from <code>rterm</code> or save the code to a .R file (say, <code>readlines.R</code>) and call</p>
  
  <pre><code>system("rscript readlines.R")
  </code></pre>
  
  <p>Then an error occurs:</p>
  
  <pre><code>Error in file(con, "r") : cannot open the connection
  Calls: readLines -&gt; file
  In addition: Warning message:
  In file(con, "r") : unsupported URL scheme
  Execution halted
  Warning message:
  running command 'rscript readlines.R' had status 1 
  </code></pre>
  
  <p>I tried a HTTP URL and there's no problem but HTTPS URL like I used always ends up in this error if the code is called from external.</p>
  
  <p>How can I fix this?</p>
  
  <p>My session info:</p>
  
  <pre><code>R version 3.1.1 (2014-07-10)
  Platform: x86_64-w64-mingw32/x64 (64-bit)
  
  locale:
  [1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252   
  [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
  [5] LC_TIME=English_United States.1252    
  
  attached base packages:
  [1] stats     graphics  grDevices utils     datasets  methods   base     
  
  loaded via a namespace (and not attached):
  [1] tools_3.1.1
  </code></pre>