Specs 0.10

Changes

• Separate CheckStorage into two variants and fix soundness issues (#203)
• Fix Merge system and add test for it (#243, #248)
• Add more examples, docs, tests, benchmarks (#249, #251, #254, #256, #258)
• Use Results to make Specs more robust (#260)
• Check code coverage with cargo-travis (#265)
• Make common::Errors atomic and more convenient (#255, #262)
• Add World::delete_all to clear the world (#257)
• Fix insertion into occupied NullStorage entry ([#269])
• Add Storage::drain method (#273)

Upgrading

Upgrading should be easy, because the only breaking changes were the CheckStorage and a few version bumps.