Loosen bundle parsing logic

[th0r]

Fixes #160

[Koslun]

@th0r if "Some bundle chunks are missing", will it be reported somewhere or be immediately apparent what bundle is missing?

My possibly unfounded concern is that errors might get too silent and cause people to draw the wrong conclusions. Where I figure that if you have quite a lot of anonymous bundles, one or two going missing from the graph could easily go unnoticed and thus ignored.

Where my assumption is that you'll be expecting the tool to perfectly match all the bundles and thus might not inspect that each bundle is there or even really look at your own list of bundle sizes, relying on this great tool instead.

[valscion]

will it be reported somewhere

Yes, this PR adds a warning console message to be printed when such chunks are analyzed. Before, the same warning used to fail the entire bundle analyze.

[th0r]

@Koslun yes, it will report about it in the console: https://github.com/webpack-contrib/webpack-bundle-analyzer/pull/181/files#diff-22404c0ae8b5efcecea3b9b27cd95271R57

The thing is this is a very rare situation - absence of some chunks. In most cases you either won't have any chunks at all (I mean physical files to parse) or will have all of them and there shouldn't be any problems.

I wonder maybe we should introduce some kind of strict: true option to address such cases?