Pass AST Plugins to each compile

[rwjblue]

This would need to detect Ember version, and when possible avoid calling registerPlugin (which mutates closure scope and requires bizarre cache clearing shenanigans). Instead of registerPlugin we would pass the plugins directly to the compile invocation (in options.plugins.ast).

Related to #116.

[rwjblue]

Implemented in #130, but needs a bit of a rebase in order to be able to land.

[fivetanley]

@rwjblue Does this mean that I would be able to write an ember addon that registers an ember-cli-htmlbars plugin and it would affect the compilation output of all the addons included in an app (vs just the app's templates)? If so I'd be happy to take a stab at rebasing #130.

[rwjblue]

@fivetanley - No it isn't quite exposing that capability, though it could be leveraged to do so (I think). This is specifically talking about _pre_registration of AST plugins taht we do, which ultimately mutates global state inside the evaluated ember-template-compiler.js. Because of that mutation, we are forced to bust the cache and re-require ember-template-compiler.js many times (resulting in non-trivial build cost, memory bloat, etc).

[rwjblue]

Implemented in #661