v0.8.0

Fixes:

• Variables from inner override variables in parents (@Daijobou, @Cerdic)
• Bootstrap issues with @at-root, self (@l2a, @Cerdic)
• @supports inside rule (@Marat-Tanalin, @Cerdic)
• SourceMapGenerator Former: invalid offset (@fabsn182)
• Number parsing (@ange007, @robocoder)

Maintenance:

• Travis test updates (@Cerdic)
• Add Bootstrap and Foundation framework tests (@Cerdic)