Bugfix for #1175 and convert textile reader to use builder.

The reader did not correctly parse inline markup. The behavoir is now as follows.

(a) The markup must start at the start of a line, be inside previous
inline markup or be preceeded by whitespace.
(b) The markup can not span across paragraphs (delimited by \n\n)
(c) The markup can not be followed by a alphanumeric character.
(d) Square brackets can be placed around the markup to avoid having
to have white space before it.

In order to make these changes it was either necessary to convert the parser to return a list of inlines or to convert the whole reader to use the builder. The latter approach whilst more work makes a bit more sense as it becomes easy to arbitarily append and prepend elements without changing the type.

Tests are accordingly updated in a later commit to reflect the different normalisation behavoir specified by the builder monoid.
Converted HTML reader to use builder. Fixes #1162.
Changed the smart punctuation parser to return Inlines rather than an Inline element and updated files accordingly
Tests updated to reflect changes to readers.

Previously normalisation was handled by the `normalizeSpaces` function. The behavoir of the builder monoid is slightly different and melds together more items such as consecutive strings and spaces adjacent to line breaks. The tests have been changed to reflect this.

All relevant tests passed when the string melding line of the builder monoid was commented out.
Merge pull request #1207 from mpickering/htmlinlines

Fix #1162, #1175 and rewrite textile and HTML backend to use the builder