Adds policy name in node details when available

[thlacroix]

For people who use policyfiles instead of roles, it would be convenient to have the policy name associated to the node directly displayed at the top of the node details.
If the node doesn't have a policy attached, the line won't be displayed.

[thlacroix]

The CI failure is not related to the code changed (can't find gem bundler (>= 0.a) with executable bundle (Gem::GemNotFoundException))

[thlacroix]

Hi @xamebax, how should I proceed with this PR ?
I'm not sure I can help solve the gem dependency issue, but as it's not related to this PR, is it still a blocker ?

[xamebax]

Hi @thlacroix, thank you for opening this PR! I'm not actively working on this project any more, but I'll try and have a look in the next few days. I think the CI error is a bundler version bug that requires updating travis.yml; I'll do that. :)