Update .gitignore
Merge branch 'SFcomparison'
updated code and paper availability note at end of paper (closes issue #2)
Merge branch 'master' into SFcomparison
Adjusted the abstract wording with regards to the state accuracy of the method (closes issue #4)

The wording did not need to be changed dramatically, especially since the main issue noted by the
referee was largely addressed by the improved Springel & Farrar (2007) comparison work (see
commits related to issue #5).