PERF: DataFrame(dict_of_categoricals)
```
from asv_bench.benchmarks.frame_ctor import *

self = FromDicts()
self.setup()

%timeit self.time_dict_of_categoricals()
1.48 ms ± 61.1 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)  # <- master
528 µs ± 2.75 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)  # <- PR
```