Merge ilc.utils into ilc.util
Comments on Stability
Stability ↦ ContextStability
Cleanup
More comments on Zipper
Try matching on context, not on term

The current code matches on an integer to recover the position. This
kind of code is harder to get right.
Fix extraction of right sibling

That's what this is. The API should be cleaned up to allow for this.
Drop commented out code
Zipper: Hole ↦ Top
Zipper: Path ↦ Context

This avoids having an alias and two names (from two metaphors) for the
same thing.
Zipper: Location/Subterm ↦ Subtree

Subtree is a single name which is appropriate both generically in the
context of Zipper and specifically inside our transformations.

This avoids the last confusing alias in our code.

I also tried to rename all occurrences of Subterm/Location in other
identifiers.
Refactor: Don't mix ifs and pattern matching

Now it's clearer that this code covers all alternatives.
Refactor

* Avoid shadowing parent (for clarity)
* Inline parent away anyway
Zipper: Hide navigation into goRight and goLeft
Merge pull request #8 from inc-lc/topic/clean-stability-2

Clean stability analysis, v2
Update to latest SBT
Merge branch 'master' into topic/from-icfp

Also fixed (by hand): src/main/scala/ilc/UnicodeOutput.scala for the
rename.