Multiple entries for component in `bower.json` main for `.html` file type

[peterblazejewicz]

This commit: https://github.com/PolymerElements/paper-icon-button/commit/95bde452267de3a5e0a0f6e34c997ed5c4d7b2f5 added light version of component - at the same time duplicating entry in bower.json main field: https://github.com/PolymerElements/paper-icon-button/blame/master/bower.json#L7-L10

The specs recommends only single entry per file type: https://github.com/bower/spec/blob/master/json.md#main So this is not an error, but a warning:

bower paper-icon-button#* invalid-meta The "main" field has to contain only 1 file per filetype; found multiple .html files: ["paper-icon-button.html","paper-icon-button-light.html"]

Still marked as invalid-meta for end users. Thanks!

[notwaldorf]

Unfortunately, we are using those multiple entries in the main field as metadata so that both elements show up in the catalog docs. So even though it's annoying as a warning, I don't think this is something that we can fix right now :(

/cc @azakus @justinfagnani @blasten