API: DatetimeIndex and PeriodIndex have same representation

[sinhrks]

Closes #7601. Made PeriodIndex to have dummy timezone representation to be consistent with DatetimeIndex, but this should be ommited?

Output after the fix

# DatetimeIndex (No change)
pd.date_range(start='2011-01-01', periods=10, freq='M')
# <class 'pandas.tseries.index.DatetimeIndex'>
# [2011-01-31, ..., 2011-10-31]
# Length: 10, Freq: M, Timezone: None

# PeriodIndex
pd.period_range(start='2011-01-01', periods=10, freq='M')
# <class 'pandas.tseries.period.PeriodIndex'>
# [2011-01, ..., 2011-10]
# Length: 10, Freq: M

[jreback]

doesn't need a tz
what I meant by consistent is the look/feel

[sinhrks]

OK. Removed tz repr from PeriodIndex

[jreback]

these are not needed - this is a mixin but all object inherit from the PandasObject which already have these defined

[sinhrks]

Ah, not noticed. Removed.

[jreback]

can this integrate some of the DatetimeIndex formatting stuff? and out in Base (while leaving the output the same)

in theory could do similarly with Series though might be much trickier

[jreback]

needs rebase
an u show the examples for both period and datetime in the top of PR

[sinhrks]

Rebased and examples are attached.

[jreback]

thanks!