chore(TypeScript): refactor objects into classes

fix: `Nil`(null, undefined) now renders as empty string
change: `parser.parseValue()` renamed to `parser.parseOutput`
change: registered tags/filters become static and shared across different liquid instances

test/e2e/render-file.ts

@@ -0,0 +1,78 @@
+var chai = require('chai')
+var mock = require('mock-fs')
+var Liquid = require('../..')
+var expect = chai.expect
+
+chai.use(require('chai-as-promised'))
+
+describe('#renderFile()', function () {
+  var engine
+  beforeEach(function () {
+    engine = new Liquid({
+      root: '/root/',
+      extname: '.html'
+    })
+    mock({
+      '/root/files/bar': 'bar',
+      '/root/files/foo.html': 'foo',
+      '/root/files/name.html': 'My name is {{name}}.',
+      '/un-readable.html': mock.file({
+        mode: '0000'
+      })
+    })
+  })
+  afterEach(function () {
+    mock.restore()
+  })
+  it('should render file', function () {
+    return expect(engine.renderFile('/root/files/foo.html', {}))
+      .to.eventually.equal('foo')
+  })
+  it('should find files without extname', function () {
+    var engine = new Liquid({ root: '/root' })
+    return expect(engine.renderFile('/root/files/bar', {}))
+      .to.eventually.equal('bar')
+  })
+  it('should accept relative path', function () {
+    return expect(engine.renderFile('files/foo.html'))
+      .to.eventually.equal('foo')
+  })
+  it('should resolve array as root', function () {
+    engine = new Liquid({
+      root: ['/boo', '/root/'],
+      extname: '.html'
+    })
+    return expect(engine.renderFile('files/foo.html'))
+      .to.eventually.equal('foo')
+  })
+  it('should default root to cwd', function () {
+    var files = {}
+    files[process.cwd() + '/foo.html'] = 'FOO'
+    mock(files)
+
+    engine = new Liquid({
+      extname: '.html'
+    })
+    return expect(engine.renderFile('foo.html'))
+      .to.eventually.equal('FOO')
+  })
+  it('should render file with context', function () {
+    return expect(engine.renderFile('/root/files/name.html', { name: 'harttle' }))
+      .to.eventually.equal('My name is harttle.')
+  })
+  it('should use default extname', function () {
+    return expect(engine.renderFile('files/name', { name: 'harttle' })).to.eventually.equal('My name is harttle.')
+  })
+  it('should throw with lookup list when file not exist', function () {
+    engine = new Liquid({
+      root: ['/boo', '/root/'],
+      extname: '.html'
+    })
+    return expect(engine.renderFile('/not/exist.html')).to
+      .be.rejectedWith(/failed to lookup \/not\/exist.html in: \/boo,\/root\//i)
+  })
+  it('should throw when file not readable', function () {
+    return expect(engine.renderFile('/un-readable.html')).to
+      .be.rejectedWith(/EACCES/)
+  })
+})