Update the file readme of demo text-classification

Fix the bug that user couldn't choose to use gpu whether or not

* Update the command download so as to show search tips when module/model can't find

Modify the command install

* Inform user the installed version of the module

* Update uncompressed model name

fix demo sequence-label

* Fix the bug that user can't download the modules

* Update the information about the command show

The command show can list the installed the modules and models.

Inform user that the input module isn't existed when one uses the command show to list a module that is not located in the computer.