Return result without callback

[s-voloshynenko]

Test coverage 100%.

[nelsonic]

@s-voloshynenko we need @plaenen's input on this. I think he wants to "bubble up" the errors...

[nelsonic]

@plaenen said: "Remove all callbacks and make it synchronous." Things to do

• if(context === null) return null;
• if(env === '') return null;
• add try/catch validateWithSchema Line15

[s-voloshynenko]

@nelsonic Ready for review, thanks!