PERF: benchmark seems to be hanging
this seems to hang on 0.19.2 / master (didn't test anything else)
```
((pandas) bash-3.2$ asv continuous v0.19.2 master --bench FrameConstructorDT
· Creating environments
· Discovering benchmarks
·· Uninstalling from conda-py2.7-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt.
·· Installing into conda-py2.7-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt.
· Running 2 total benchmarks (2 commits * 1 environments * 1 benchmarks)
[  0.00%] · For pandas commit hash 3853fe6d:
[  0.00%] ·· Building for conda-py2.7-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt...
[  0.00%] ·· Benchmarking conda-py2.7-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt
[ 50.00%] ··· Running frame_ctor.FrameConstructorDTIndexFromOffsets.time_frame_ctor
```
