Add FAQ entry about indexing and Rosetta examples

This patch adds few FAQ entries regarding the motivation behind the Fortran
array indexing convention and also adds side-by-side Python/NumPy vs. Fortran
array indexing examples into the Rosetta Stone chapter.
Use better formulations, thanks to John Pask
Remove unnecessary empty lines in tables
Use Latex to represent math
Use pngmath to typeset Latex
Rearrange the sections a bit for clarity
Fix a typo in NumPy indexing
Merge pull request #13 from certik/indexing

Add FAQ entry about indexing and Rosetta examples