No env3

[Whytehorse]

The install from source instructions say:

# build tensorflow
source ~/env3/bin/activate

But when running that I get: $ source ~/env3/bin/activate bash: /home/ben/env3/bin/activate: No such file or directory

And then all steps after that fail.

[yarrseni]

You have to create a virtual environment, for particular one yo've mentioned, it would be

`mkdir -p ~/env3/

cd ~/env3

virtualenv venv`

You could read more on Python virtual environments here: py-docs/venv

[Whytehorse]

OK, thank you. I didn't need to use a virtual environment. Perhaps the instructions could be updated to show that is optional and add the steps you mentioned.