* Fix isomorphic-fetch IHeaders.get signature
According to the specification, get can return null, so this should be explicit, since TS 2.0.
* Remove trailing whitespace
* Fix Lint
* Use "lib" in tsconfigs instead of "target".
Only add "dom" to libraries that need it. This is determined by a script, so many libraries that have "dom" maybe should not.
* Update new-package and readme
* Add back "target" where necessary