Issue 29 add linter, closes #29

[swoloszynski]

What

• A "linter" is a type of software/library that will automatically check our code for style consistency and keep things clean.
• Added JS Hint
• Added JS Hint default configs in the .jshintrc file
• Customized a few settings in the config file (separated, at the top of the file)
• Added an npm command for linting all code files (app.js, all src and test files) - npm run lint
• Included linting in test command npm test
• Cleans up the files to resolve any linting complaints

How to test

• Remove a semi colon or otherwise break the rules, then run npm test and npm run lint to see that it highlights the error. Change it back, rerun, and see that the linter is happy.