add new filtering behavior
add getWeakSuffixesMap
add weakSuffixes logic to getBuildPaths
jshint: hush!
replace old filtering behavior with new, since it seems that it doesn't break anything
allow per-technology cache based on target file name
Tests for weak maps
Pass correct suffix to getBuildResultChunk
Pass output and opts to getBuildPaths

Required for bem-core i18n techs
Merge pull request #432 from bem/weak-map

Add weak suffixes support