Split Windows and Linux instructions apart
Merge pull request #94 from townxelliot/rewrite-getting-started-1284

Split Windows and Linux instructions apart
Clean up sample text and links
Add SIMD sample description
Update links for new crosswalk-samples version
Update unwieldy paragraph
Add SIMD sample icon
Add note about minimum version of Crosswalk + arch required for SIMD

Only works on beta Crosswalk on x86.