This PR does two things:

1. I moved `package.json` into the root directory. Why? We are using `npx` from the `Makefile` which is executing usually under the root directory. If we install `node_modules` in `src/js` then these invocations don't see `node_modules` and install an extra copy of the packages. So we want `node_modules` in the root directory. node wants to put `node_modules` in the same directory as `package.json` hence I moved `package.json`. I also updated the build rules so that any recipe that uses `npx` has a dependency on `node_modules/.installed`.
2. We invoke `file_packager.py` from both the Makefile (in two places) and from `build_pkg`. There has been some drift in which options are applied in the two places. I extracted the common options and the task of locating the `file_packager.py` script into `tools/file_packager.sh`. I also shortened the make rules for `distutils.data` and `test.data` and made some minor updates to the dev docs about `file_packager.py`.
MAINT Improvements to node and file_packager invocations. This PR does two things:

1. I moved `package.json` into the root directory. Why? We are using `npx` from the `Makefile` which is executing usually under the root directory. If we install `node_modules` in `src/js` then these invocations don't see `node_modules` and install an extra copy of the packages. So we want `node_modules` in the root directory. node wants to put `node_modules` in the same directory as `package.json` hence I moved `package.json`. I also updated the build rules so that any recipe that uses `npx` has a dependency on `node_modules/.installed`.
2. We invoke `file_packager.py` from both the Makefile (in two places) and from `build_pkg`. There has been some drift in which options are applied in the two places. I extracted the common options and the task of locating the `file_packager.py` script into `tools/file_packager.sh`. I also shortened the make rules for `distutils.data` and `test.data` and made some minor updates to the dev docs about `file_packager.py`.
package:
  name: asciitree
  version: 0.3.3
source:
  sha256: 4aa4b9b649f85e3fcb343363d97564aa1fb62e249677f2e18a96765145cc0f6e
  url: https://files.pythonhosted.org/packages/2d/6a/885bc91484e1aa8f618f6f0228d76d0e67000b0fdd6090673b777e311913/asciitree-0.3.3.tar.gz
test:
  imports:
  - asciitree

package:
  name: asciitree
  version: 0.3.3
source:
  sha256: 4aa4b9b649f85e3fcb343363d97564aa1fb62e249677f2e18a96765145cc0f6e
  url: https://files.pythonhosted.org/packages/2d/6a/885bc91484e1aa8f618f6f0228d76d0e67000b0fdd6090673b777e311913/asciitree-0.3.3.tar.gz
test:
  imports:
  - asciitree
