Reporter: TapReporter align actual with expected

When comparing two strings, it is significantly easier to spot the
difference when they are aligned. This change pads the label for
`actual` with a couple of spaces so that the actual value is printed at
the same indentation as the expected value. Previously the expected
value was right shifted by 2 characters...

Closes #107.

Author: rwjblue

lib/reporters/TapReporter.js

@@ -48,7 +48,7 @@ export default class TapReporter {
 
     if (error.hasOwnProperty('actual')) {
       var actualStr = error.actual !== undefined ? ('"' + JSON.stringify(error.actual, null, 2).replace(/"/g, '\\"').replace(/\n/g, '\\n') + '"') : 'undefined'
-      console.log(`  actual: ${actualStr}`)
+      console.log(`  actual  : ${actualStr}`)
     }
 
     if (error.hasOwnProperty('expected')) {

test/unit/tap-reporter.js

@@ -85,15 +85,15 @@ describe('Tap reporter', function () {
 
     emitter.emit('testEnd', data.actualUndefinedTest)
 
-    expect(spy).to.have.been.calledWith('  actual: undefined')
+    expect(spy).to.have.been.calledWith('  actual  : undefined')
   }))
 
   it('should output actual value for failed assertions even it was falsy', sinon.test(function () {
     var spy = this.stub(console, 'log')
 
     emitter.emit('testEnd', data.actualFalsyTest)
 
-    expect(spy).to.have.been.calledWith('  actual: "0"')
+    expect(spy).to.have.been.calledWith('  actual  : "0"')
   }))
 
   it('should output expected value for failed assertions even it was undefined', sinon.test(function () {