Docs: Fix Pyphen dictionaries link
Merge pull request #47 from Smylers/Pyphen_link_fix

Docs: Fix Pyphen dictionaries link
Prefix 'hyphens' in the user agent stylesheet
Document how to disable automatic hyphenation. Fix #48.
Document how to build the documentation.
Fix URL escaping of image references from CSS.
Fix #49: Division by 0 on dashed or dotted border smaller than one dot/dash.
Fix #44: bad interaction of `page-break-before/after: avoid` and floats.
Changelog for v0.17.1
Add support for multiple backgrounds (except for the shorthand.)
Upgrade the background shorthand for multiple layers.
Add `background-attachement: local`, same as scroll.

Since we have no scrolling mechanism,
local and scroll are treated the same.
The background shorthands accepts values for -clip and -origin.
Allow percentages in background-size.
Prepare background-position internals for Level 3 syntax.
Work around floating point errors when shrink-to-fit = max-content.
Upgrade background-position to Level 3.
Parse background-size in the background shorthand.
Prepare for L3 background-repeat.
Add syntax for two keywords in background-repeat.