algorithms.mesh: WarpPoints interface

An interface to Warp vtk meshes from a displacement field. Uses scipy.map_coordinates interpolation.

PS. We should consider adding the following code:
```
from traits.etsconfig.api import ETSConfig
ETSConfig.toolkit = 'null'
```
at the root of nipype imports. As we don't use the gui support of enthought.traits, the toolkit can be set to null and some errors are prevented.