Added Timestamp for posts

[maljes]

Closes #124

[jp-hoehmann]

Ddd

[jp-hoehmann]

Whoops.

[jp-hoehmann]

Thanks for the PR. Here is a few things to check before merging this:

• It would be nice to be able to see the time as well.
• The PostsComponent currently breaks slightly for some devices, when the <aside> is open. Impacted are for example Notebooks with non-retina WXGA (1366x768) displays, as well as pretty much all retina devices with screen sizes between 12" and 13". To fix this, either change the layout, or shorten the date representation (f.e. by making it relative: "1d" is both shorter and easier to read than "26.10.2017").
• The <[matTooltip]> on the date currently informs me about who likes the Post. It should instead give additional information about the date, for instance the date in an unambigouos format (f.e. with the month spelled out) along with the date of the last edit.
• The display of the date occludes the name of the Profile in the PostComponent on phones in portrait mode.
• Where possible, please keep the HTML independent of the design and please please please don't copy-paste code, for it is bound to cause great despair.
• The class you are looking for is .pad-right-sm, iirc.
• storyType.created_time is the raw string as fetched from the API. Its better to use story.createdTime so you dont have to rely on automatic typecasts to create the Date for you.

Other than that, this seems pretty good.