added virtualenv option to show python version [Enhancement]

[jerome-diver]

I add an option to be able to show python version from virtualenv activate.

[Syphdias]

Hi, @jerome-diver, I'm a bit confused about all the changes you make. I think you only want to change prompt_virtualenv. So all your changes would probably be in segments/virtualenv
Could you take another look at your changes?

[jerome-diver]

@Syphdias yes sure, i need one or two days, i'm vry busy actually. I will follow the correct proceed also.
And yes, it is a little change (3 lines i think) for add an option to segment/virtual_env to be able to read python version when inside a python virutalenv environment.
I did allready an other one PR, but i have no time this day to check that... i'll be back for that.
Thank you

[jerome-diver]

hi @Syphdias, i done this pull request instead: #1241
and it seems to be ok.
But i can not see the change inside master official repo. How to make this officialy accepted ? It should be fine if at the next update i can hold this change on my config and i see other users asked for this change. Yu can also delete this one who failed due to my fault...
What do you think about that change ?