Created Unassigned: @import statement [71]

Since [LESS v1.4.0](http://lesscss.org/features/#variables-feature-import-statements) it is possible to use variables in @import statements.
I'm using BundleTransformer.Core v1.8.29 and the same version of BundleTransformer.Less and have an exception
> File '/Common/Content/overrides/styles/@{bootstrapPath}/variables.less' not exist

Same code compiles without any errors by nodejs (v0.10.26) less compiler (v1.7.0).