Add support for virtual environments

[Chris7]

Docs will be on another MR

[codecov-commenter]

Codecov Report

Attention: 30 lines in your changes are missing coverage. Please review.

Comparison is base (b113ef6) 77.12% compared to head (63a6951) 77.31%.

Files	Patch %	Lines
wooey/tasks.py	80.70%	7 Missing and 4 partials :warning:
wooey/tests/scripts/venv_pandas_test.py	0.00%	11 Missing :warning:
wooey/models/core.py	88.00%	2 Missing and 1 partial :warning:
wooey/api/forms.py	66.66%	1 Missing and 1 partial :warning:
wooey/tests/test_virtual_envs.py	96.61%	1 Missing and 1 partial :warning:
wooey/admin.py	83.33%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #392 +/- ## ========================================== + Coverage 77.12% 77.31% +0.19% ========================================== Files 139 143 +4 Lines 4856 5017 +161 Branches 649 666 +17 ========================================== + Hits 3745 3879 +134 - Misses 969 989 +20 - Partials 142 149 +7 ``` | [Flag](https://app.codecov.io/gh/wooey/Wooey/pull/392/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wooey) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/wooey/Wooey/pull/392/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wooey) | `77.25% <83.85%> (+0.17%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wooey#carryforward-flags-in-the-pull-request-comment) to find out more.

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