build(deps): bump rxjs from 5.5.12 to 6.4.0

[dependabot-preview]

Bumps rxjs from 5.5.12 to 6.4.0.

Changelog

Sourced from rxjs's changelog.

6.4.0 (2019-01-30)

Bug Fixes

• ajax: Fix case-insensitive headers in HTTP request (#4453) (673bf47)
• bundle: closure to not rewrite polyfills for minification (#4487) (a1fedb9)
• bundle: don't export operators twice (#4310) (2399f6e)
• combineLatest: improve typings for combineLatest (#4470) (40c3d9f)
• compat: remove internal from import locations (#4498) (a6c0017), closes #4070
• endWith: ability to endWith different types (#4183) (#4185) (83533d1)
• fromEventPattern: improve typings for fromEventPattern (#4496) (037f53d)
• Observable: Fix Observable.subscribe to add operator TeardownLogic to returned Subscription. (#4434) (f28955f)
• subscribe: Deprecate null starting parameter signatures for subscribe (#4202) (c85ddf6)
• combineLatest: support passing union types (ffda319)
• from: support passing union types (eb1d596)
• withLatestFrom: support passing union types (1e19a24)
• zip: support passing union types (0d87f52)
• multicast: support returning union types from projection (e9e9041)
• exhaustMap: support returning union types from projection (ff1f5dc)
• merge: support union type inference for merge operators (c2ac39c)
• catchError: support union type returns (8350622)
• switchMap: support union type returns (32d35fd)
• defer: support union types passed (5aea50e)
• race: Update typings to support proper return types (#4465) (0042846)
• VirtualTimeScheduler: rework flush so it won't lose actions (#4433) (d068bc9)
• WebSocketSubject: fix subject failing to close socket (#4446) (dcfa52b)

Features

• shareReplay: Add configuration object for named arguments, and add argument to support unsubscribing from source observable by refCount when all resulting subscriptions have unsubscribed. The default behavior is to leave the source subscription running.
• mergeScan: Add index to the accumulator function (#4458) (f5e143d), closes #4441
• range: accept one argument (#4360) (a388578)
• takeWhile: add an inclusive option to the operator which causes to emit final value (#4115) (6e7f407)

Performance Improvements

• internal: optimize Subscription#add() for the common case (#4489) (bdd201c)
• internal: use strict equality for isObject() (#4493) (fc84a00)
• Subscription: use instanceof to avoid megamorphic LoadIC (#4499) (065b4e3)

6.3.3 (2018-09-25)

Bug Fixes

... (truncated)

Commits

• d3e7e3f chore(publish): 6.4.0
• f5e143d feat(mergeScan): Add index to the accumulator function (#4458)
• 0ee4fbe docs($browser): Added description to webSocketSubjectConfig and example. (#4299)
• 02a39b1 docs($browser): Created examples for using switchAll operator (#4242)
• a98c0e1 docs(external resources): First version of external resources (#4057)
• 0fd8707 feat(shareReplay): add config parameter (#4059)
• a388578 feat(range): accept one argument (#4360)
• 6e7f407 feat(takeWhile): add an inclusive option to the operator which causes to em...
• 573adca test(dtslint): add dtslint test for forkjoin obsrevable (#4093) (#4414)
• 1af81fd feat(docs) add doc for timeinterval operator (#4508)
• Additional commits viewable in compare view

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[dependabot-preview]

Superseded by #908.