Remedy errant spacing in ImageMagic compose cmd building.

[kylev]

CoffeeScript trims leading/trailing spaces from multi-line strings, so we ended up with filenames and flags occasionally jammed against the geometry portion.

[kylev]

0.4.2 is essentially non-functional right now. It builds commands like this:

composite -geometry 428x60+0+0sprite/nytimes_hover_2x.png build/sprites.png build/sprites.png.tmp && mv build/sprites.png.tmp build/sprites.png

Note: there should be a space after the 428x60+0+0 and before sprite/nytimes_hover_2x.png.

[kylev]

Looking back through old PRs... Looks like this bug still happens if you enable downsampling. It'll build an invalid (crashing) command line.