Merge pull request #6028 from jreback/series_infer

BUG: Bug in Series construction of mixed type with datelike and an integer
PERF: vbenches for DataFrame.apply
PERF: perf enhancements for DataFrame.apply (GH6013)
TST: check appropriate tests for apply
PERF: allow apply to use the fast-path in mixed type frames except where datelike
      are present