Documenation Improvements

[eliasinul]

Store (hdf5)

• include documentations on how to resolve AttributeError: Attribute 'block2_items_variety' does not exist in node:

Source: usually indicates one of these conditions:

• the HDF5 node was written incompletely or got corrupted
• the same key was written before with a different internal structure
• pandas/PyTables is trying to read an old incompatible fixed-format object
• the key contains a partially overwritten object