The <tt> tag is deprecated, according to:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/tt

The <code> tag is proposed as a replacement. It has the same intented
semantics: an inline block of code:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/code

Closes #41.

This is not simply fixing up spelling and grammar, but a full (ish)
review of English language strings and translation structure. This lays
the groundwork for a more formal translation round at a later date.

Some of the phrasing will inevitably be coloured by en_GB preference,
but I don't feel any shame about that.

Removed some visitor uses in mia, and moved some leftover mia templates from process to mia/. refs: #11

Adding Django related i18n template tags so the string can be extracted
and filled into the language related .po files.