CLN: period boundscheck warnings
follow up to fix warnings in https://github.com/pydata/pandas/pull/11263#issuecomment-149641296

gr8. ping on green.
 rebase/repush as conda had some issues
 @jreback - this is passing now
 thanks!
 @chris-b1 if you'd do one more ....thanks!

```
cythoning pandas/tslib.pyx to pandas/tslib.c
warning: pandas/tslib.pyx:4257:25: Use boundscheck(False) for faster access
warning: pandas/tslib.pyx:4258:26: Use boundscheck(False) for faster access
warning: pandas/tslib.pyx:4260:56: Use boundscheck(False) for faster access
warning: pandas/tslib.pyx:4261:22: Use boundscheck(False) for faster access
warning: pandas/tslib.pyx:4275:25: Use boundscheck(False) for faster access
warning: pandas/tslib.pyx:4276:26: Use boundscheck(False) for faster access
warning: pandas/tslib.pyx:4278:56: Use boundscheck(False) for faster access
warning: pandas/tslib.pyx:4279:22: Use boundscheck(False) for faster access
```
