2.3.0

CHANGES:

• Albatross-daemon: discover and provide root policy with the available system
  resources (#190 @hannesm @reynir @PizieDust)
• Vmm_core.Policy.usable: check that block size, if present, is non-negative
  (#192 @hannesm)
• BREAKING: rename vm to unikernel (#192 @hannesm)
• Document Vmm_trie (#192 @hannesm)
• Parse /proc/pid/status less strict (#193 @Firobe)