title: Force install.packages()
body: <p>Is it possible to install a package in R forcefully ?</p>
  
  <pre><code>&gt; install.packages("gsubfn")
  Installing package(s) into ‘/home/sebastian/R/x86_64-unknown-linux-gnu-library/2.14’
  (as ‘lib’ is unspecified)
  --- Please select a CRAN mirror for use in this session ---
  Loading Tcl/Tk interface ... done
  Warning message:
  In getDependencies(pkgs, dependencies, available, lib) :
    package ‘gsubfn’ is not available (for R version 2.14.2)
  </code></pre>
  
  <p>In this case the package requires R >= 2.15 and I only have R 2.14.2 . 
  Wondering whether I can do a force install . </p>