Move __version__ from string to tuple type.

[Matteo Nastasi]

Using a tuple to describe the version a correct comparison will be possible.

Currently a comparison between "1.2.10" and "1.2.2" return wrong result because is using lessicographical ordering.

From ipython:
In [1]: (1, 2, 10) > (1, 2, 2)
Out[1]: True

In [2]: "1.2.10" > "1.2.2"
Out[2]: False

Moreover, we should increase the minor version when running from Git.

[Michele Simionato (michele-simionato)]

Changing this will break the sed scripts we are using. Why don't we just introduce a function converting the version into a tuple?

Something like

def version_tuple(version_str):
    return tuple(map(int, version_str.split('.')))