DOC: fix doc build warnings

- indentation error in the option docstring
- link to options page that has moved
- select_dtypes docstring
TST: additional network error catching (test_html/test_spam_html)
Merge pull request #7713 from jorisvandenbossche/doc-fixes3

DOC: fix doc build warnings
BUG: DatetimeIndex.__iter__ creates a temp array of Timestamp (GH7683)
PERF: DatetimeIndex.__iter__ now uses ints_to_pydatetime with boxing
remove code dup in tslib.ints_to_pydatetime
Merge branch 'issue7683' of github.com:yrlihuan/pandas into issue7683