Update dependency webpack to v1.15.0

[mend-for-github-com]

This PR contains the following updates:

Package	Type	Update	Change
webpack	devDependencies	minor	1.13.1 -> 1.15.0

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Release Notes

webpack/webpack

v1.15.0

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Note: webpack 1 do no longer receive bugfixes/features. Please upgrade to webpack 2.

Bugfixes:

• check for own property when adding modules from chunk (IE8)
• support uglifyjs mangle options

Features:

• wrap module function in parentheses

v1.14.0

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Bugfixes:

• fix this context for AMD require when combined with async commons chunk
• update core dependency, which fixes a SourceMap bug
• update node.js core libs

v1.13.3

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v1.13.2

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