Ergonomic language features and lib cleanup

+ let bindings
+ where bindings
+ do notation

I explored enough of the alternative language design space and decided
that we should commit fully to Lambda style. That means no more highly
tacit/concatenative point-free/partial programs as default. We'll keep
taking advantage of those capabilities when it makes sense, but the
library will continue to see massive overhauls.

lib/bytes.tri

@@ -3,9 +3,11 @@
 
 bytesNil? = emptyList?
 
-bytesHead = matchList nothing (h _ : just h)
+bytesHead =
+  matchList nothing (h _ : just h)
 
-bytesTail = matchList nothing (_ r : just r)
+bytesTail =
+  matchList nothing (_ r : just r)
 
 bytesLength = length
 bytesAppend = append