documentation: developer documentation update

Updated the developer documentation to include:

- General patch submission philosophy

- Basic runtime debugging using strace(1) and ldd(1)

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
documentation: clarify architecture as x86_64

Change a x86 reference to x86_64.

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
Merge pull request #6 from cbrune/docs

Docs