Add TOML support

[LyndonArmitage]

Addresses #49

Uses toml4j to add TOML support for the version 0.4.0 of TOML.

At original time of writing the specification for TOML 0.5.0 was not released. There are few potential libraries that can be used that support 0.5.0, this is one such example that uses ANTLR.

Other libraries may also be better suited than the initial one chosen, that is up for debate.

Note: I have used Jetbrains annotations in this commit, if that is not desired I can remove them and stick with standard Java 8 methods of ensuring method contracts when it comes to null values.

[cescoffier]

Also, did you sign the Eclipse CLA?

[LyndonArmitage]

I have not signed the CLA as of yet, I will have a read and sign if I agree to it.