[refactor] use a class attr instead of a const for desc
[refactor] removing tasks.rb
[refactor][feature] dynamic task def injections

Changed all task definitions to look like each other - not wrapped in a module
This is so that readers of src wont get confused when they just want to write more tasks.

The DSL object treats the default task dir the same way it would for an injected path.
i.e.: it's the same logic through & through, the only difference is that the default task
      path gets loaded on initialization of the object

Also too the time to remove the consts in the tasks
[refactors] updating & simplifying cli, app & runner
[refactor] just use fx overrides for descriptions
[feature] make task_path a class_option & list custom tasks in CLI too
[bugfix] rake returns an array...?
[cleaning] backtrace logs. can read. nicely.
[release] correct Gemfile.lock version
[feature] cli prints out task script fx name too

Task::task() was made public for this; added test
Merge pull request #9 from behance/custom-dsl

Dynamic task injections into DSL