Update devDependencies

Travis issue: https://travis-ci.org/nodeca/mincer/builds/4808570
Making lazy templates implementation more elegant

Instead of define `fn.solve`, now it's necessary to define a method
`toString` int the template class and a function property called
`lazySource`.
Documentation included.
Including new tests to check Lazy Templates
Just to remove some jshint complains
Fix code comment

- coffee-script -> jade
fixed current travis state
Removing jshint relaxation
partial tests cleanup & lint cleanup
Improving tests

- Making them pass through Lint;
- Improving readability.