Update CaimAn code

[ecobost]

Right now we use my own fork of CaImAn which was last updated on Nov 2017. I freezed to avoid introducing bugs in our pipeline; we should definitely still keep it frozen but maybe create a cajal/CaImAn (rather than ecobost/CaImAn) and also update the code to be a most recent version. This will most probably require some changes to the functions in pipeline.utils.caiman_interface to deal with whatever new changes they have made.
The benefits is that the most recent CaImAn code would have fixed some bugs and improved on clarity and efficiency.