creates DEVICES object for device lookup, and listDevices()
implements getDevice()
implements case independent lookup for exists(), get(), and getDevice()
implements default behavior - returns all for get() and getDevice()
adds postupdate and get-specs scripts to package.json
fixes crash caused by remaking an existing directory
adds tests
adds tests
removes source(), and renames getDevice() to device()
fixes logic to check for length of arguments instead of input type in get() and device()
changes checking of directory existence to use fs.exists instead of try catch statement
updates tests to not use underscore
Merge pull request #1 from doc-metrix/feature/deviceLookup

merge Feature/device lookup with master