Validate storage keys' length and improve doc

[alcuadrado]

Closes #557

[lgtm-com]

This pull request introduces 1 alert when merging 95ec40a into 4bbb6e3 - view on LGTM.com

new alerts:

• 1 for Unused variable, import, function or class

[coveralls]

Coverage increased (+0.02%) to 95.114% when pulling 91e2d43 on state-manager-buffer-lengths into 59743f2 on master.

[holgerd77]

Just a note on first look: "Remove LGTM warning" is not an optimal commit message since this hides the change itself being done and is not really readable in the commit message.

[holgerd77]

(sorry, a bit nit-picking, but "Remove unused import in StateManager" or something would just be more expressive).

[holgerd77]

@s1na I think these changes/improvements make a lot of sense and would have a tendency to approve and merge (after another PRs CI has been run through and I can update this branch). If you have any objects in between while reading let me know.

[s1na]

Looks good to me

[alcuadrado]

Just a note on first look: "Remove LGTM warning" is not an optimal commit message since this hides the change itself being done and is not really readable in the commit message.

That's a good point @holgerd77! I'll write more descriptive commit messages in the future :)