Segment: add strictness to Offset,Segment,OffsetEnvelope
Segment: change getEnvelope calculation

Float divisions out of the inner calculation.
R2: use a specialized HasTrie instance for R2

For diagrams with a large number of transforms, this can be 5-10% faster and
use slightly less memory.
SizeSpec2D: add strictness and unbox fields.
Merge pull request #132 from JohnLato/strictness-optimizations

Strictness optimizations