Add note about AUIPC+JALR range in RV64

Update .travis.yml (riscv#502)

Clarify offset range in RV64I (riscv#501)

Claire Wolf pointed out in email to [isa-dev] that "The 2048 points missing on the higher [end] are "tacked on" on the lower end". This PR adds this detail to the previous commentary.

RV64 -> RV64I

Add commentary about multi-hit/failing to SFENCE.VMA

fixing api_key format

Add VA canonicalization check to Translation Process section

This is just a clarification, since the requirement is stated
in the Sv39 and Sv48 sections.

Clarify that FCVT instructions signal inexact

Move VALEN check to the top of Translation Process section

No semantic change.

Incorporate Andy Glew's comments