Busted down first version of available space

This will just treat all sibling elements as being on the same line, and then
will give you the remaining width, prior sibling height (or parent height) that
can be used in a text layout attempt.

Also provides a sanity checking spec for the overall method as it grows.
Refactoring available_space
Generate layout from text block and compare height
Adding with_siblings helper
Should have been using right from sibling, not width
Hackery to see how TextBlockFitter works with single line
Extend to treat resulting layouts a collection, not singular
Determining where to split text from failed layout attempt
Return layout with position from fitter
Spike for spilling over to second text layout
Merge branch 'master' into mad_flow
With update_current_position, don't need absolute_right overrides
Merge branch 'master' into mad_flow
Move FittedTextLayout in containing class
Name methods for shrinking layout width
Text block position overrides need different names

As it stood reusing names from the slot didn't work out, since sub-slots would
get bad override calls.

We'd like to get rid of these or harmonize them in some way, but that's a task
for another day.
Extract named methods from fitting algorithm
Use contents_alignment instead of new overrides

Previously thought that we couldn't make the right behavior with only using the
contents_alignment method, but turns out we can. Before was simply missing the
necessary overrides to let the TextBlock customize all the required absolute_*
methods in question, which originally stalled out my attempts to use the
existing hook.
Fix DSL/mock specs up to run, reveals a number of SWT failures though...
Merge pull request #2 from PragTob/mad_flow

Fix DSL/mock specs up to run, reveals a number of SWT failures though...