Initial implementation of map function and associated tests

Implementation of a map function in index.js.  Associated unit tests
for the map function are located in the tests folder.
Add code coverage for test script

Update npm dependencies and test script to check code coverage using
coveralls and istanbul
moved chai dependency to devDependencies
added jshint to devDependencies
Merge pull request #1 from mradamh/map-implementation

Initial implementation of map function and associated tests