Tried to get everything to an rc.0 of the very latest version,
which required some research in some cases about the published
versions.  For example, some packages had version histories like:

```
...
  1.0.3-winr.2               January 20th, 2015
  1.0.3-winr.3               February 24th, 2015   installed
  1.0.3                      March 17th, 2015      installed
  1.0.4-anubhav.0            August 6th, 2015
  1.0.4-plugins.0            July 22nd, 2015
  1.0.5-galaxy.0             July 17th, 2015
```

In this case, I would bump the version from `1.0.4-plugins.0`
to `1.0.5-rc.0`, skipping `1.0.4`.

Tried to get everything to an rc.0 of the very latest version,
which required some research in some cases about the published
versions.  For example, some packages had version histories like:

```
...
  1.0.3-winr.2               January 20th, 2015
  1.0.3-winr.3               February 24th, 2015   installed
  1.0.3                      March 17th, 2015      installed
  1.0.4-anubhav.0            August 6th, 2015
  1.0.4-plugins.0            July 22nd, 2015
  1.0.5-galaxy.0             July 17th, 2015
```

In this case, I would bump the version from `1.0.4-plugins.0`
to `1.0.5-rc.0`, skipping `1.0.4`.

Tried to get everything to an rc.0 of the very latest version,
which required some research in some cases about the published
versions.  For example, some packages had version histories like:

```
...
  1.0.3-winr.2               January 20th, 2015
  1.0.3-winr.3               February 24th, 2015   installed
  1.0.3                      March 17th, 2015      installed
  1.0.4-anubhav.0            August 6th, 2015
  1.0.4-plugins.0            July 22nd, 2015
  1.0.5-galaxy.0             July 17th, 2015
```

In this case, I would bump the version from `1.0.4-plugins.0`
to `1.0.5-rc.0`, skipping `1.0.4`.

Tried to get everything to an rc.0 of the very latest version,
which required some research in some cases about the published
versions.  For example, some packages had version histories like:

```
...
  1.0.3-winr.2               January 20th, 2015
  1.0.3-winr.3               February 24th, 2015   installed
  1.0.3                      March 17th, 2015      installed
  1.0.4-anubhav.0            August 6th, 2015
  1.0.4-plugins.0            July 22nd, 2015
  1.0.5-galaxy.0             July 17th, 2015
```

In this case, I would bump the version from `1.0.4-plugins.0`
to `1.0.5-rc.0`, skipping `1.0.4`.

Tried to get everything to an rc.0 of the very latest version,
which required some research in some cases about the published
versions.  For example, some packages had version histories like:

```
...
  1.0.3-winr.2               January 20th, 2015
  1.0.3-winr.3               February 24th, 2015   installed
  1.0.3                      March 17th, 2015      installed
  1.0.4-anubhav.0            August 6th, 2015
  1.0.4-plugins.0            July 22nd, 2015
  1.0.5-galaxy.0             July 17th, 2015
```

In this case, I would bump the version from `1.0.4-plugins.0`
to `1.0.5-rc.0`, skipping `1.0.4`.

Tried to get everything to an rc.0 of the very latest version,
which required some research in some cases about the published
versions.  For example, some packages had version histories like:

```
...
  1.0.3-winr.2               January 20th, 2015
  1.0.3-winr.3               February 24th, 2015   installed
  1.0.3                      March 17th, 2015      installed
  1.0.4-anubhav.0            August 6th, 2015
  1.0.4-plugins.0            July 22nd, 2015
  1.0.5-galaxy.0             July 17th, 2015
```

In this case, I would bump the version from `1.0.4-plugins.0`
to `1.0.5-rc.0`, skipping `1.0.4`.

The comments are not related to the fix, they are just for future
reference.

The fix is that having an "own" property named `constructor` should
not disqualify an object from being considered an "instance of some
class."  Instead, we should detect that an object like
`{constructor: ...}` is a plain object by noting that
`!(x instanceof x.constructor)`.

1. Add `addAssets` API to `package.js`
2. Rename `getSourcesFunc` to `getFiles` in internal code
3. Changed `PackageAPI#sources` to `PackageAPI#files` with a new structure that
   has separate objects for assets and sources
4. Added some tests for different error conditions
5. The same file can now be a source and an asset

Fixes #5137

Fixes #5137

Conflicts:
	History.md
	packages/babel-compiler/.npm/package/npm-shrinkwrap.json
	packages/babel-compiler/package.js
	packages/ecmascript/package.js
	packages/sha/package.js
	tools/upgraders.js

This reverts commit e6bc9413f3f7313225dc4ae87e2e25a85ca0c59a.

Fixes #4756