Added splat handling

[jaen]

As per issue #69 I refactored the splat handling into it's own branch and added tests.
All the test pass.

I have several reservations about the code though and I'd like your input:

• the splats maintain only relative order of how they appear in the template, that is they get bunched up in the back of the tag in order they appeared; It may be better that they kept absolute order (ie. if you have a splat before an attribute, then the splat attributes would appear before the attribute in the output)
• the make_render_splat function is a bit of a hack to pass the Haml.compile test, I'm not sure if that's the right way to do that, but I figured that if render_attributes function has the option to use a custom escaper, then render_splats shoul do so too and that's the way it occured to me to code it
• the test pass, but I'm not sure if the code is robust enough

[aaronblohowiak]

Sorry, I made this have conflicts with other branches that I merged in. If you can make this merge cleanly again, I will merge it ASAP.