Fix `grunt dist` under Bower by separating docs into separate task

BS3 commits: a9b7ba419a3f0b0ef0fc71a553d323c2d07af604
Fix 14411 by setting JSON Content-Type for Gist API request

BS3 commits: 71c2c372f6a14eae4bf7ae51958f770583bc2ccc
grunt

BS3 commits: e7d5905f38f5bd4c10425733e7b78941550a9cf2