Simplified app development. Refs #8

This code allows to use a really simple approach to pre-load tasks and
reduce the code in any PyBossa app. This commit does not have the unit tests.
Unit Tests for pybossa.run method. Refs #8
Unit Tests for PyBossa on different endpoint. Closes #8
Merge pull request #9 from PyBossa/issue-8-simplify-app-dev

Issue 8 simplify app dev