Use local uglifyjs

It's safer to use the local in node_modules, so that
developers don't need to have uglifyjs installed
globally.

Makefile

@@ -2,7 +2,7 @@
 all: test
 
 site:
- ./node_modules/.bin/browserify entry.js --exports require | uglifyjs > web/content/assets/js/jison.js
+ ./node_modules/.bin/browserify entry.js --exports require | ./node_modules/.bin/uglifyjs > web/content/assets/js/jison.js
  cd web/ && nanoc compile
  cp -r examples web/output/jison/