message: Install documentation: adds note for virtual env with fish shell
diff: @@ -131,7 +131,8 @@ Take the following steps to install TensorFlow with Virtualenv:
  commands:
  <pre>$ <b>source ~/tensorflow/bin/activate</b> # bash, sh, ksh, or zsh
  - $ <b>source ~/tensorflow/bin/activate.csh</b> # csh or tcsh</pre>
  + $ <b>source ~/tensorflow/bin/activate.csh</b> # csh or tcsh
  + $ <b>. ~/tensorflow/bin/activate.fish</b> # fish</pre>
  The preceding <tt>source</tt> command should change your prompt
  to the following:
  