* DataFile Update

* Update learning.py

* Update search.py

* Update test_learning.py

* Update test_text.py

* Add files via upload

* Update text.ipynb

* Update search-4e.ipynb

* Create CONTRIBUTING.md

The link to "Pseudocode algorithm (pdf)" was pointing to https://github.com/aimacode/pseudocode/blob/master/algorithms.pdf, which was causing the 404 error. The name of the file algorithms.pdf was changed to aima3e-algorithms.pdf by @ctjoreilly in commit 80286be. Edited the link to reflect that change and point to a valid URL.