v0.1.0a40: Some optimizations in postprocessing and other changes.

• Created a more optimized contour generating function, which should show significant speedups when extracting or merging cells.
• Various optimization for generate_hypersphere_masks, which should improve testing.
• Refactored generate_hyperdisc_masks from generate_hypersphere_masks.
• Made a minor optimization in expand_view.
• Refactor wavelet_denoising to use extract_neurons instead of keeping duplicated code.
• Fixed SGE install on Travis CI so that testing on SGE can continue.
• Redisabled testing on SGE with Travis CI due to the significant slowdown.