Convert backend code to ES modules

Bundling code now with Rollup for its flat bundling and tree shaking
support. Front end code still goes through Webpack for browser support.

lib/common/expression-parser.js

@@ -1,6 +1,6 @@
 "use strict";
 
-const parsimmon = require("parsimmon");
+import parsimmon from "parsimmon";
 
 // Turn escaped characters into real ones (e.g. "\\n" becomes "\n").
 function interpretEscapes(str) {
@@ -22,7 +22,7 @@ function interpretEscapes(str) {
   });
 }
 
-function map(exp, callback) {
+export function map(exp, callback) {
   if (!Array.isArray(exp)) return callback(exp);
 
   let clone;
@@ -271,12 +271,12 @@ const lang = parsimmon.createLanguage({
   }
 });
 
-function parse(str) {
+export function parse(str) {
   if (!str) return null;
   return lang.Expression.tryParse(str);
 }
 
-function stringify(exp, level = 0) {
+export function stringify(exp, level = 0) {
   if (!Array.isArray(exp)) return JSON.stringify(exp);
 
   const opLevels = {
@@ -360,7 +360,7 @@ function stringify(exp, level = 0) {
   }
 }
 
-function parseLikePattern(pat, esc) {
+export function parseLikePattern(pat, esc) {
   const chars = pat.split("");
 
   for (let i = 0; i < chars.length; ++i) {
@@ -377,8 +377,3 @@ function parseLikePattern(pat, esc) {
   }
   return chars.filter(c => c);
 }
-
-exports.parse = parse;
-exports.stringify = stringify;
-exports.map = map;
-exports.parseLikePattern = parseLikePattern;