ENH/BUG: partial string indexing with PeriodIndex
Merge pull request #7043 from sinhrks/pslice

ENH/BUG: partial string indexing with PeriodIndex
DOC: v0.14.0.txt edits
BUG: Escape `<` and `>` in info _repr_html_

Closes https://github.com/pydata/pandas/issues/7105