Use lock in dd.read_hdf
Use lock in dd.read_hdf

Fixes #760

jakirkham/dask,dask/dask,jcrist/dask,pombredanne/dask,vikhyat/dask,jcrist/dask,mikegraham/dask,blaze/dask,mraspaud/dask,chrisbarber/dask,jakirkham/dask,vikhyat/dask,cowlicks/dask,ContinuumIO/dask,blaze/dask,mraspaud/dask,ContinuumIO/dask,gameduell/dask,cpcloud/dask,dask/dask,mrocklin/dask,mrocklin/dask,pombredanne/dask