feat(stream)!: Allow mutable iteration

[epage]

This is a step towards #72

v0.4.7

json/basic/canada       time:   [10.272 ms 10.308 ms 10.347 ms]
json/verbose/canada     time:   [32.539 ms 32.714 ms 32.893 ms]
json/dispatch/canada    time:   [8.9747 ms 8.9926 ms 9.0118 ms]
json/streaming/canada   time:   [10.612 ms 10.667 ms 10.726 ms]

main (6747a8d)

json/basic/canada       time:   [10.234 ms 10.254 ms 10.274 ms]
json/unit/canada        time:   [9.5594 ms 9.5917 ms 9.6248 ms]
json/verbose/canada     time:   [30.371 ms 30.442 ms 30.517 ms]
json/dispatch/canada    time:   [8.8071 ms 8.8344 ms 8.8651 ms]
json/streaming/canada   time:   [9.7001 ms 9.7262 ms 9.7552 ms]

#274

json/basic/canada       time:   [10.231 ms 10.253 ms 10.279 ms]
json/unit/canada        time:   [9.3250 ms 9.3526 ms 9.3808 ms]
json/verbose/canada     time:   [29.832 ms 29.891 ms 29.957 ms]
json/dispatch/canada    time:   [8.4980 ms 8.5093 ms 8.5211 ms]
json/streaming/canada   time:   [10.007 ms 10.044 ms 10.081 ms]

[coveralls]

Pull Request Test Coverage Report for Build 5476297501

• 64 of 120 (53.33%) changed or added relevant lines in 8 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.4%) to 50.832%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/binary/bits/mod.rs	3	4	75.0%
src/combinator/parser.rs	1	2	50.0%
src/token/mod.rs	13	14	92.86%
src/trace/internals.rs	0	1	0.0%
src/ascii/mod.rs	12	24	50.0%
src/stream/mod.rs	32	72	44.44%

Totals
Change from base Build 5448486419:	0.4%
Covered Lines:	1253
Relevant Lines:	2465

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💛 - Coveralls