Issue #17 - breaking changes on master

[cowboy-bebug]

Following what's mentioned in paritytech/substrate#10403,

• Default is removed for PlayerStruct (to avoid deriving default values for T::AccountId) and
• OptionQuery is used for BracketIndexKeyMap and BracketKeyValueMap storage items

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Changes (in the order of commits):

• 3b64a3e: run cargo fmt
• 293c850: peg / freeze upstream dependencies at a revision
  • specifying version seems a little bit meaningless for us since we're pointed directly to the latest upstream master
  • instead, using rev to peg at a commit hash
  • chosen this commit, paritytech/substrate@3dc9842, as it was the highest commit without breaking changes
• c18cbba: point to the commit of the breaking changes, paritytech/substrate@55cd07a, and fix any errors
  • removed deriving Default for PlayerStruct as mentioned in Remove Default bound for AccountId paritytech/substrate#10403
  • use OptionQuery for the storage items dealing with T::AccountId
  • add the recently introduced MaxConsumers for mock (as empty for now)
  • small refactor for fn pop() since the storage items now return Option
• 18d608b: point to the latest master

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Closes #17.

[darkfriend77]

great!