Bump rand from 0.4.2 to 0.6.4

[dependabot-preview]

Bumps rand from 0.4.2 to 0.6.4.

Changelog

Sourced from rand's changelog.

[0.6.4] - 2019-01-08

Fixes

• Move wasm-bindgen shims to correct crate (#686)
• Make wasm32-unknown-unknown compile but fail at run-time if missing bindingsg (#686)

[0.6.3] - 2019-01-04

Fixes

• Make the std feature require the optional rand_os dependency (#675)
• Re-export the optional WASM dependencies of rand_os from rand to avoid breakage (#674)

[0.6.2] - 2019-01-04

Additions

• Add Default for ThreadRng (#657)
• Move rngs::OsRng to rand_os sub-crate; clean up code; use as dependency (#643) ##BLOCKER##
• Add rand_xoshiro sub-crate, plus benchmarks (#642, #668)

Fixes

• Fix bias in UniformInt::sample_single (#662)
• Use autocfg instead of rustc_version for rustc version detection (#664)
• Disable i128 and u128 if the target_os is emscripten (#671: work-around Emscripten limitation)
• CI fixes (#660, #671)

Optimisations

• Optimise memory usage of UnitCircle and UnitSphereSurface distributions (no PR)

[0.6.1] - 2018-11-22

• Support sampling Duration also for no_std (only since Rust 1.25) (#649)
• Disable default features of libc (#647)

[0.6.0] - 2018-11-14

Project organisation

• Rand has moved from rust-lang-nursery
  to rust-random! (#578)
• Created The Rust Random Book
  (source)
• Update copyright and licence notices (#591, #611)
• Migrate policy documentation from the wiki (#544)

Platforms

• Add fork protection on Unix (#466)
• Added support for wasm-bindgen. (#541, #559, #562, #600)
• Enable OsRng for powerpc64, sparc and sparc64 (#609)
• Use syscall from libc on Linux instead of redefining it (#629)

RNGs

• Switch SmallRng to use PCG (#623)
• Implement Pcg32 and Pcg64Mcg generators (#632)
• Move ISAAC RNGs to a dedicated crate (#551)
• Move Xorshift RNG to its own crate (#557)

... (truncated)

Commits

• 4336232 Merge pull request #686 from dhardy/master
• 1d07496 Fix changelogs and bump rand_os version number
• 5142481 Merge remote-tracking branch 'origin/master' and update changelog
• afc9d9a Merge pull request #670 from akash-fortanix/sgx-target
• e1e4005 Update changelog
• 1ad20a7 Generalise WASM tests
• 94efb40 Remove remaining WASM remnants from rand to rand_os
• f7bfa1a rand_os: use run-time failure on unsupported WASM platforms
• 42ece4f Document and correct usage of new rand_os "feature"
• 1d97fa1 remove winapi feature
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #19.