DOC: resolved mistakes in examples series

[MichielStock]

Adjusted some docstring examples.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@2229c26). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master   #15625   +/-   ##
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  Coverage          ?   90.99%           
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  Files             ?      143           
  Lines             ?    49306           
  Branches          ?        0           
=========================================
  Hits              ?    44868           
  Misses            ?     4438           
  Partials          ?        0

Impacted Files	Coverage Δ
pandas/core/generic.py	96.25% <ø> (ø)
pandas/core/series.py	94.91% <ø> (ø)
pandas/conftest.py	94.11% <100%> (ø)

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[jorisvandenbossche]

@MichielStock There were some PEP8 issues (lines too long, we test for that on Travis), but fixed those before merging.

Thanks!