Move asset code generation logic to babel-template

Reviewed By: rafeca

Differential Revision: D8661779

fbshipit-source-id: 00799ee1fd76f764634ac1b43b7be823afe80231

Bump metro@0.40.0

Summary:
This new version of metro replaces the `getProjectRoots()` config param by `getProjectRoot()` (which is used as the main folder for calculating relative paths of files, etc) and `getWatchFolders()` (which is used to know which files/folder to crawl when starting metro).

More info: facebook@3bdf386

[skip-ci]

Reviewed By: yungsters, mmmulani

Differential Revision: D8538986

fbshipit-source-id: 2afc33950334a278364debb39f34ef0fe0535894

Bumping Metro to 0.39.1

Reviewed By: rafeca

Differential Revision: D8418105

fbshipit-source-id: 66032deb53f46a388b81233e8d00d7af6a2c7fa7

Bump metro@0.39.0

Reviewed By: mjesun, davidaurelio

Differential Revision: D8380199

fbshipit-source-id: 6b9e3aa343e8d0526a3c42d5ea266c44428d31f8

Bump metro@0.38.1

Reviewed By: jeanlauliac

Differential Revision: D8248753

fbshipit-source-id: aa6d0da4e96e8b4109b6b5bca050614ec1860fc2

Bump metro@0.38.0

Reviewed By: davidaurelio

Differential Revision: D8235787

fbshipit-source-id: a22802c829920e7e182a9aae70bd69a6446d5f8f

Upgrade Metro to 0.37.2

Reviewed By: rafeca

Differential Revision: D8223545

fbshipit-source-id: fdaacbb514e2947b9244cb55ef9170af55ba2f60

Bump Metro to 0.37.1

Reviewed By: rafeca

Differential Revision: D8038396

fbshipit-source-id: 33fe5499825653f205bdb588ff4c7fa232602f24

Bump metro@0.37.0

Reviewed By: jeanlauliac

Differential Revision: D7988114

fbshipit-source-id: aeaed94cb89a929ab5079af957bfccd9fd7ebd83

Metro v0.36.1

Summary: contains fixes to `metro-babel-register` necessary for node 6 compat (as supported by React Native)

Reviewed By: mjesun

Differential Revision: D7788437

fbshipit-source-id: 805b185dd970bf376f11664aeabea0bb8ac94b8b