Ver 0.8.0

Moved: tzdata/* to data/tzdata.dat (binary format)
Added: math.Vector#to_list, math.Matrix#to_list
Fixed: unicode.normalize passed NormalizationTest.txt (Unicode.org)
Fixed: ZipRandomReader crushes when timezone not given
Removed: webimage/giflib/*: removed unused code
Changed: Raises error when Map#op_index failed (No keys found)
Fixed: 1 << 31 gives wrong answer