Add concise API

[sameoldmadness]

Something like:

BEM.decl('block', {
  // i-bem stuff
  template: function (ctx) { /* bh stuff */ }
}):

BEM.append('anchor', { bem: 'json' });

[sameoldmadness]

CSS styles could be also defined in js.

Consider two options: inline styles or inject css into page.