Overflow should check sign of exponent.

Fix SIMD page fault by using aligned load

Related to discussion in #83

Issue75stopwhendone

Add MemoryBuffer and MemoryStream

Iterative parse optimization

Issue31optimizeitoa

Performance boost a lot!

It is not very useful for iterative parsing as the worst case of heap
size is O(n) where n is number of character in JSON, for the worst
synthetic cases. This is reasonable and should not create stack overflow
security problem as in recursive parsing.

Supplemental documents for iterative parsing

Iterative Parsing (for issue #35)