Initial commit
Added .gitignore
Splits the dataviews subpackage out from imagen and fixes imports

This commit introduces the dataviews package, which consists of
data containers for storing data across n-dimensions, along with
plotting code to visualize the views and an IPython extension to
embed the plots within a notebook. The commit also contains
changes to imports within imagen to reflect the addition of the
dataviews subpackage.
Added empty_element property to easily generate blank overlays

Fixes bug associated with overlaying SheetStacks with non-matching
dimension values, where empty frames would have to be created with
the existing bounds but could not as the __mul__ operator was
implemented at the superclass level, which does not implement bounds.
Added centering option to DataCurvePlot
Changed the way DataOverlays compute xlim and ylim
Introduced the %params line magic to Imagen for parameter inspection
Implemented the equality operation for the BoundingBox class
Fixed calculation of ylim in SheetStack.sample
Fixed implementation of equality operator for BoundingBoxes
Improved the functionality and robustness  of the %params IPython magic
IPython extension now centers HTML display for all dataviews
Initial commit of transform.py to dataviews including HCS and colorize
Added DataHistogram to dataviews
Added PERCENTAGE_SIZE variable to extension for more flexible display
Fixed bug in add_dimension method of NdIndexableMapping
Fixed bug when ylim lower and upper bound were equal in DataStack
Split out static method to find input_sheet_slice
Added cmap2rgb and split operations to transform
Fixed unit tests ImportError for IPython version <0.13