docs(mkdocs): Convert README to MkDocs

This is a rewrite of documentation from README using MkDocs. MkDocs allow to build a full documentation using markdown files. It is supported by ReadTheDocs.
docs(mkdocs): Add proper site title
docs(readme): Add docs link to README
fix(sortable): Use valid scope to check sortable model
fix(watchers): Avoid useless column generation due to initialization of watchers

This also display more events in demo at initialization time, loading of data is now made after events logging registration.

From angularJS $scope documentation:

After a watcher is registered with the scope, the listener fn is called asynchronously (via $evalAsync) to initialize the watcher.

In rare cases, this is undesirable because the listener is called when the result of watchExpression didn't change.

To detect this scenario within the listener fn, you can compare the newVal and oldVal. If these two values are identical (===) then the listener was called due to initialization.

Close #217
perf(data): Abort loops when row or task has been found

 When removing data the loop can be stopped when the correct row or task has been found
fix(movable): Fix invalid row switching

This fixes the method to retrieve row from mouse.

close #227
docs(mkdocs): Fix small issues

This fixes small issues related to file locations.