Fix the complete key in the IPython debugger

[asmeurer]

It should now be tab instead of N (or whatever the first letter of the color scheme is).

Fixes #213.

[asmeurer]

Based on the order, I think the CI is getting stuck on test_py_kernel_1 (why was -v removed from the CI flags?). For me locally with the same environment it XPASSes.

[codecov-commenter]

Codecov Report

Base: 72.59% // Head: 72.56% // Decreases project coverage by -0.02% :warning:

Coverage data is based on head (01cc577) compared to base (0d82450). Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #229 +/- ## ========================================== - Coverage 72.59% 72.56% -0.03% ========================================== Files 25 25 Lines 7988 7991 +3 ========================================== Hits 5799 5799 - Misses 2189 2192 +3 ``` | [Impacted Files](https://codecov.io/gh/deshaw/pyflyby/pull/229?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deshaw) | Coverage Δ | | |---|---|---| | [lib/python/pyflyby/\_interactive.py](https://codecov.io/gh/deshaw/pyflyby/pull/229?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deshaw#diff-bGliL3B5dGhvbi9weWZseWJ5L19pbnRlcmFjdGl2ZS5weQ==) | `51.83% <0.00%> (-0.12%)` | :arrow_down: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deshaw). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deshaw)

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[asmeurer]

I guess it was just spurious.

[dshivashankar1994]

Approved the changes. @Carreau, Please merge.