Fix for #37 in Index.md

Also style change - changed all commands in 'single quotes' to markdown `code` format.
Updated to include x/x commands as per #37
Update index.md

Added a short example chaining flags together for x/x.
Update gdb_summary.html

Added example of x/x with several flags together
Update gdb_summary.md

Updated with `x/format (var/address)` instead of "examine"
Merge pull request #43 from mrecachinas/master

Fix for #37 in Index.md