Basic ToUnicode support (fixes copy-n-paste from the PDF)
Allow for profiling using line_profiler
Move functionality contained in the split(), glyphs() and widths() methods
of SingleStyledText to Paragraph.render()

This avoids creation of SingleStyledText instances for each word in a
SingleStyledText, and thus the initialization in widths() and glyphs() does
not need to be performed over and over again.

The RFIC example still renders, but the output is broken. Also, some
features such as tabs are currently being ignored.
Encapsulate refactored typesetting code into generators
Remove obsolete code
Make hyphenation work again
Encapsulate duplicated code (kerning/ligatures)
the cached decorator should not ignore keyword args
Pre-load the hyphenation dictionary to be able to properly benchmark
Tiny optimization
More verbose execution time reporting
Make Fields work again
Refactor to avoid confusion between the two spans
Make justification work again
Make nested flowables work again
Fix splitting of paragraphs across containers (messy!)
Some refactoring
Remove empty spans at the end of a line
Create the (span, item) pairs in ParagraphState so that Flowables don't
need to take care of that
Pass the space glyph and width to GlyphsSpan on init