BUG: infer_freq results in None for hourly freq with timezone
Found fix #7318 was incorrect. It works for lower frequencies than dates, but not for higher freq than hours.
 I couldn't detect as test cases are also incorrect...

This should work for all the freqs with timezones.

NOTE: I couldn't use normal `tslib.tz_convert` which returns incorrect results maybe caused by DST. Applying `tslib.tz_convert_single` can work though.

thanks
 hmm, this broke in 3.4: https://travis-ci.org/pydata/pandas/jobs/26939770
 this is broken in 2.7 as well, just bisected it
 @sinhrks going to revert this
 @cpcloud also putting 3.4 on the main build (and 3.2 on experimental, just to have it run)
 cool, just reverted d91d145
