v0.6.0

Besides some cleanup, this version introduces changes related to the options and flags you can pass to the cli.

• many of the named flags have been removed. For instance subwasm diff -a r1.wasm -b r2.wasm now becomes subwasm diff r1.wasm r2.wasm, subwasm get --url http://foo:9933 becomes subwasm get http://foo:9933.
• new root level flag: --json will allow producing json output. This changes the behavior of the ìnfo` command