Move doc generation commands to script file

They were getting too large already, and I want to add more.

bin/generate-docs

@@ -0,0 +1,6 @@
+#!/bin/bash -ex
+
+rm -r docs || true
+
+cd test/ciao
+node ../../node_modules/ciao/bin/ciao -c ../ciao.json . -d ../../docs

package.json

@@ -13,7 +13,7 @@
     "ciao": "node node_modules/ciao/bin/ciao -c test/ciao.json test/ciao",
     "coverage": "node_modules/.bin/istanbul cover test/unit/run.js",
     "audit": "npm shrinkwrap; node node_modules/nsp/bin/nspCLI.js audit-shrinkwrap; rm npm-shrinkwrap.json;",
-    "docs": "rm -r docs || true; cd test/ciao; node ../../node_modules/ciao/bin/ciao -c ../ciao.json . -d ../../docs"
+    "docs": "./bin/generate-docs"
   },
   "repository": {
     "type": "git",