Added code for downloading the PWT version 8.0 data set.
Added code for grabbing the depreciation rates data.
Refactored to include a base_url for accessing data files.
Refactored by wrapping code for downloading pwt and depreciation rate data into separate functions.
Added some success messages.
Refactored two functions into a single function.
Fixed a small typo!
Added some code for extracting .dta files from the zip archives.
Added functionality for loading PWT data into a Pandas Panel object.
Refactored the download functions into separate funcs.
Functions for getting specific data sets are now private. User should call public wrapper function.
The load_pwt_data function now returns a Pandas Panel object!
BUG FIX: invalid url when downloading from the web.
Added a print statment for quick debugging.