Cache loss and display it in the live_info widget

I've added caching of the loss and use it to diplay the loss in the live_info widget.

Calculating the loss could be an "expensive" calculation and in this way, no time is wasted.

LGTM, I like the feature

added 3 commits

• a511f93b - add 'cache_loss' decorator
• e64e4927 - use 'cache_loss' decorator in learners
• a80f4a71 - display the loss with 'live_info'

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added 1 commit

• 440cad9e - simplify Learner2D plotting in the notebook

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assigned to @jbweston

added 6 commits

• 440cad9e...b5b81acc - 2 commits from branch master
• 6d5cc14e - add 'cache_loss' decorator
• b44ff418 - use 'cache_loss' decorator in learners
• 3e56870a - display the loss with 'live_info'
• d5774ffc - simplify Learner2D plotting in the notebook

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enabled an automatic merge when the pipeline for d5774ffc succeeds

merged

mentioned in commit 953ff845

mentioned in issue #125 (closed)