refresh .juliabox, .ipython on ebs volumes
ami_recentness call take instance id

used during scale up decisions to exclude instances with older amis
let user added ipython extensions persist

ref #153
Merge pull request #163 from tanmaykm/tanmaykm

backup/restore and auto-scaling changes
ipython changes to fix notebook export. fixes #162

IPython was broken as `mistune` got updated to `0.5`.
JuliaBox IPython fork fixed and docker build updated.

Could not move to current IPython branch as notebook upgrade doesn't seem to be working fine yet,
and upgraded JuliaBox notebooks won't open on the ipython released version (which will be the
most common version installed by users locally).
Merge pull request #164 from tanmaykm/tanmaykm

ipython changes to fix notebook export. fixes #162
deleted unused script
fix bug in ami recentness detection
ability to send commands to cluster members
added cairo & graphviz dependencies and packages
add sbin to path for Cairo
Merge pull request #168 from tanmaykm/tanmaykm

added cairo & graphviz, plus misc changes
added patchwork
Merge pull request #169 from tanmaykm/tanmaykm

added patchwork