Adds skip to content links #60.

[Lucas-Mc]

Adds links at the top of each page to skip users directly to the content. This is useful for those using Lynx and Screen Readers as mentioned in #60. Fixes part of #60.

[tompollard]

Are you confident that this is doing what we want to be doing? I'm not clear how these "skip to content" links are intended to be used, and I've not been able to test.

Note to self to check out these links:

• https://accessibility.oit.ncsu.edu/it-accessibility-at-nc-state/developers/accessibility-handbook/mouse-and-keyboard-events/skip-to-main-content/
• http://web-accessibility.carnegiemuseums.org/code/skip-link/

[Lucas-Mc]

I used this link here as a guide for the CSS: https://webaim.org/techniques/css/invisiblecontent/ and I used the old website as a guide for the implementation. It has this:

<p class="u2">
<a href="#content" class="u2">Skip to content</a> |
<a href="#mainmenu" class="u2">Jump to navigation menu</a></p>

and then this later:

<a id="content"></a>

[tompollard]

Okay, cool, if you're good with it then I'm happy. Please could you drop the CSS into the stylesheet? I'll then merge.