Bump im from 10.2.0 to 12.3.3

[dependabot-preview]

Bumps im from 10.2.0 to 12.3.3.

Release notes

Sourced from im's releases.

12.3.1

Changed

• Unsafe chunks have been separated out into the sized-chunks crate, which is now a dependency of im.

Changelog

Sourced from im's changelog.

[12.3.3] - 2019-03-11

Fixed

• A number of issues were fixed where Vector's size table would get out of
  sync with the node structure if exercised too much and cause erroneous
  behaviour. (#72, #74)
• Comprehensive generative tests were added to test all data structures through
  more unexpected code paths.

[12.3.2] - 2019-03-05

Changed

• Clone constraints on all data structures, as well as relevant constraints on
  maps and sets, have been relaxed where possible, so that you can now construct
  empty instances and call most query methods without requiring values implement
  Clone etc. (#63)

Fixed

• Constructing an empty Vector will not allocate any heap memory, instead
  deferring allocation until you perform an operation that would increase its
  length. (#65)
• Some bugs arising when using Vector::append repeatedly were fixed. (#67,
  #70)

[12.3.1] - 2019-02-19

Changed

• Unsafe chunks have been separated out into the sized-chunks crate, which is
  now a dependency of im.

[12.3.0] - 2019-01-15

Added

• singleton methods have been deprecated and renamed to unit.
• Vector::chunks and Vector::chunks_mut have been deprecated and renamed to
  leaves and leaves_mut to avoid confusion with Vec::chunks. (#50)

Fixed

• Fixed an issue where the HashMap draining iterator might access uninitialised memory leading to
  undefined behaviour. (#60)
• Fixed multiple issues in Vector::split_off and Vector::append that would cause lookup errors
  and unexpectedly unbalanced trees. (#55).

[12.2.0] - 2018-10-12

... (truncated)

Commits

• 35712f1 (cargo-release) version 12.3.3
• 779f742 Comprehensive tests validate the reality of the size table at each step.
• 7dca278 Add CI builds in release mode to catch future debug_assert! gaffes.
• b6ea902 Changelog for recent bug fixes.
• 51bb80a Revert feature flag to stay working on stable.
• 1d80f4e Merge pull request #76 from krobelus/index-in
• 2470fd4 Merge pull request #73 from krobelus/issue_72
• 417fa4b Merge pull request #75 from krobelus/issue_74
• 1e8c3e4 Fix RRB target index lookup
• 286949c Update RRB size table after draining in push_chunk
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #28.