Fixed bug in antsRegistration outputs. Close #944

Now, I'll be looking at #883.
enh: add FAST option for SPM12
fix: set default number of threads for ITK programs to 1
enh: add threading option to Eddy
sty: white spaces
fix: environment variable must be a string
tst: fix spm tests
ref: eddy to remove setting inputs
Merge pull request #954 from oesteban/bug/FixANTSoutputs

Fixed bug in antsRegistration outputs
tst: updated test for eddy
tst: add generation for removing a test when package is not found
tst: removed test skipping code - can be overwritten easily by adding a named test
sty: removed old interface code writer
Merge pull request #957 from satra/enh/misc

Enh/misc -  a few cleanup and enhancement changes
bug, added 'priors/' prefix to -p flag
added prefix to output
removed priors directory, all files will be in current directory
Merge branch 'master' of https://github.com/armaneshaghi/nipype