feat(Has read & update methods):

read() takes path to json and passes it in to callback
update() takes path to external-scripts and path to package.json, edits external-scripts. Also takes optional callback.
fix(refactored read & update methods)
Merge branch 'feat-update-method' into develop
feat(uninstall-method)

uninstall method takes 2 paths and optional callback as its args
Merge branch 'feat-uninstall-method' into develop
fix(update & uninstall): made code that was used in both methods into a function
feat(test cases): refactored fixtures, added test case to update()

Now checks case for if file is already in external-scripts
fix(renamed update): update() is now install()

Avoids ambiguity as removing a script from external-scripts.json is technically updating that file.
feat(read me): Added documentation for methods
Merge branch 'fix-method-refactor' into develop
Merge branch 'develop'