Fmriprep

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* FIX: Downloads from OSF, remove data downloader (now in niworkflows)
* FIX: pybids was missing in the install_requires
* FIX: Deprecated ``-S``/``--subject-id`` tag
* ENH: Accept subjects with several T1w images (114)
* ENH: Documentation updates (130, 131)
* TST: Re-enabled CircleCI tests on one subject from ds054 of OpenfMRI
* ENH: Add C3D to docker image, updated poldracklab hub (128, 119)
* ENH: CLI is now BIDS-Apps compliant (123)

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* ENH: Grabbit integration (113)
* ENH: More outputs in MNI space (99)
* ENH: Implementation of phase-difference fieldmap estimation (91)
* ENH: Fixed bug using non-RAS EPI
* ENH: Works on ds005 (datasets without fieldmap nor sbref)
* ENH: Outputs start to follow BIDS-derivatives (WIP)

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* ENH: Added Docker images
* DOC: Added base code for automatic publication to RTD.
* Set up CircleCI with a first smoke test on one subject.
* BIDS tree scrubbing and subject-session-run selection.
* Refactored big workflow into consistent pieces.
* Migrated Craig's original code