Add a number to each selection in Sublime Text 2, incremented once per selection

I recommend the plugin Text Pastry. The Number Sequence command is the one you need.

I prefer to use the Insert Nums command:

Text Pastry has a build in support for the Insert Nums syntax by
providing three numbers separated by one space:

N M P

N: the start index.

M represents the step size which will be added to the index for
each selection.

P must be > 0 and will be used to pad the index with
leading zeroes.