Removed elemental submodule.
Removed .gitmodules file since we have no submodules.
Squashed 'src/elemental/' content from commit 22f7e1c

git-subtree-dir: src/elemental
git-subtree-split: 22f7e1cb0c508eff1f80fd1b46dad72c5262d449
Merge commit 'dfce7c25e6063a8768982aef4062270b5697982f' as 'src/elemental'
Merge pull request #109 from justusc/master

Add Elemental subtree