Fixed repr error for DictExpr
Merge pull request #155 from fegin/master

Fixed repr error for DictExpr
Add Tutorial to README and update installation

Add link to the tutorial in the GitHub wiki.

Update installation to use the spartan-array/spartan repository instead of rjpower/spartan.
Merge pull request #156 from rgardner/update-readme

Add tutorial to README and update installation instructions
Clean up some outdated code and comments.
Merge pull request #157 from fegin/master

Clean up some outdated code and comments.
Merge branch 'master' of github.com:spartan-array/spartan