Sassdown should have functional test coverage

[winstromming]

Problem:

• Manual testing is currently required to ensure the correct processing of output by the module, which is prone to user error.

Objective:

• Write a series of functional tests to be instanced using Mocha, asserting that the core methods within the module are functioning correctly and returning the desired output.
• Write another series of tests that assert both gulp and grunt, in addition to node streams, can return the desired output when processes are spawned on the command line.

[winstromming]

Spawning and executing a child process for gruntfile and gulpfile output testing:

var exec = require('child_process').exec

describe('grunt', function () {
  before(function (done) {
    exec('./node_modules/.bin/grunt --base ./ --gruntfile ./tests/gruntfile.js', done)
  })
})
describe('gulp', function () {
  before(function (done) {
    exec('./node_modules/.bin/gulp --gulpfile ./tests/gulpfile.js', done)
  })
})