Multi-arch alternative rewrite

[dubo-dubon-duponey]

This is an alternative to #12, taking the approach mentioned before (and that I now prefer for my own use):

• ditches upstream extension mechanism entirely
• use logdna source from the clone instead of pulling from github through glide
• get rid of the build.sh shenanigans and onbuild triggers

Gives:

• simplified, more grokable build pipeline
• faster to buid, more cacheable
• no binary dependency, only source
• easier to patch/fork upstream

To build it, just call ./build.sh (it will fail pushing of course, read the script).

[dubo-dubon-duponey]

Incidentally cut the fat from the resulting image (from 16MB down to 9MB).

[dubo-dubon-duponey]

Closing for lack of interest.