ENH: Add custom JavaScript to HTML docs
ENH: Add copybutton.js

This JavaScript snippet will add a >>> button to the top right of source
code examples, such that it automatically removes  the `>>>` and the
`...` characters.
DOC: Rephrase credit
DOC: Add scikit-learn's license for copybutton.js
MAINT: Move license to licenses folder
Merge pull request #286 from ElDeveloper/copybutton

Add button to hide >>> and ... from code examples