Documentation about pipelines
Some refactoring
Some tests for objects
Big refactorin, new function to execute pipes
Removed more code :)
added some notes
removed unused import
Refactoring
Execution part moved in its own module
Added some devices (csv I/O, json I/O, simple filtering and transformation)
Better globals for Expression.eval()

Plus, inverted default order of locals/globals
Fix
Test for CSV I/O
More tests on simple pipes
Now deepcopying rows before transforming..
More description in the README