Support infinite responses in bodyWrapper

[chunweii]

Fixes #245.

[coveralls]

Coverage: 95.678% (+0.8%) from 94.828% when pulling 2b1b1d6 on chunweii:infinite-bodywrapper into 1e30c27 on gavv:master.

[gavv]

Thanks for PR! Here are some comments.

[gavv]

Thanks a lot for PR!

Big work and I think the code is correct.

bodyWrapper was an intricate piece from the beginning...

I pushed a follow-up commit with an attempt to refactor it a bit: 73a6521

What I changed:

• added comments

• renamed "origReader" to "httpReader" and "cancelFunc" to "httpCancelFunc", to make it clear that they correspond to original HTTP response

• renamed "currReader" to "memReader" and "origBytes" to "memBytes", to make it clear that they correspond to in-memory storage

• refactored Read: now it explicitly states three cases: rewinds are disabled, reading from HTTP; rewinds are enabled, reading from HTTP; reading from memory

• when Read is reading from memory, it now returns cached error only after reading the whole body, for more strict emulation of original response

• renamed "readNext" to "httpReadNext" and "readFull" to "httpReadFull", to make it clear that they read from HTTP

• Rewind now resets reader only when it makes sense

• in httpReadNext, we now correctly handle the case when when error is returned, but n > 0; in this case we should still append bytes to memory

• in httpReadFull is refactored a bit

• I renamed TestBodyWrapper_InfiniteResponses to TestBodyWrapper_Memory, because it does not actually test infinite responses, but instead tests how response is stored into memory in various cases

• I reworked TestBodyWrapper_PartialRead so that it actually requests more bytes than returned (request 10, got 4), otherwise reads were not really partial

[gavv]

Another follow-up commit: 924c915 - improvements and refactoring of body wrapper tests.

[gavv]

A few more follow-up commits:

• 70e3c1b - expand comments
• e3afff4 - bug fix
• fa46eaa - expand tests

In addition, I created a few new issues for expanding tests even further:

• Improve bodyWrapper Rewind test #377
• Improve bodyWrapper GetBody test #378
• Add bodyWrapper test for error handling with rewinds disabled #380

[gavv]

One more:

• Free memory after rewinds are disabled in bodyWrapper #381