Use --strictNullChecks for safer code base

[harunurhan]

In the release notes of v2 you can read about the feature. It is enforces for null/undefined checks where it's possible to have based on the variable types.

There is also ! operator, when you're sure that a variable is non-null, to be used where compiler couldn't guess. For example: As far as I checked this kinda happens a lot with our current JSONSchema which has all possible things optional inside and not strict enough so before we have to change it as well.

http://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-0.html

In the future, or even maybe with this one we can also enable other strict rules, such as --noImplicitAny and --noImplicitThis.