Added kwargs timeit_repeat and timeit_number to Benchmark. Defaults to 3 and 1000 respectively.
Added timeit_repeat and timeit_number as columns in the summary file.
Updated README
fix: result was not being calculated as per call and would depend on timeit_number

fixes issue with tuples not being converted to list in ObservableList
Merge branch 'master' of https://github.com/lobocv/pyperform