Add Github's Objective-C .gitignore file.

This prevents .DS_Store and xcuserdata files/dirs from causing
the AFNetworking submodule to always have `(untracked content)`
listed in `git status`.
use the weakself/strongself pattern to fix AFHTTPClient not being released

see AFNetworking issue #581
Merge pull request #612 from Madefire/afhttpclient_no_dealloc

fix for AFHTTPClient not being released
Minor reformatting of weak/strong self pattern for network reachability callbacks
Break retain cycle for background tasks
Using __weak reference in setCompletionBlock:
Using conventional weak/strong self pattern to break retain cycle in background tasks
Merge pull request #588 from natestedman/master

Add Github's Obj-C .gitignore
Updates AFJSONRequestOperation to allow JSON parsing options since it is now using the NSJSONSerialization class by default
Renaming parseOptions property to JSONReadingOptions

Updating documentation for JSONReadingOptions property
Merge branch 'master' of github.com:AFNetworking/AFNetworking
Removing excess whitespace
[Issue #592][Issue #600] Changes the logic of UIImageView -setImageWithURLRequest:placeholderImage:success:failure: such that if the success block is specified, the default behavior of self.image = image is not executed. This allows for full customization over any post-processing on the image, or the animation to be used when setting the image.
[Issue #603] Removing duplicated runloop scheduling of outputStream
[Issue #565] Checking for kCFStringEncodingInvalidId from CFStringConvertIANACharSetNameToEncoding() before getting NSStringEncoding with CFStringConvertEncodingToNSStringEncoding, which may otherwise lead to unexpected behavior
[Issue #599] Refactoring AFHTTPClient to remove unnecessary JSON / plist serialization functions, logging any error that may arise.
Document change for next version.
[Issue #591] Attempts to fix crash caused by incorrect calculation of range when reading data into buffer.

When the current buffer isn't large enough to store the data,
AFNetworking attempts to fill the current buffer with as much data as
it can holds and leaves the remaining data to the next buffer.

There is a bug when calculating the range to read from data in the next
buffer. The `_phaseReadOffset` is set correctly but the `[data length]`
is not adjusting correctly to the offset. This causes `getBytes:range:`
to complains that it attempts to get bytes that are out of range.

An attempted fix is done here by adjusting the range (Also adjust to
check against `_phaseReadOffset` instead of `range.length`.

As I am modifying some critical section, a detail review might be
required.

I am sending this pull request so as to facilitiate the review process,
but if you are already in review of the issue and the solution, you can
ignore my pull and close it. Thanks!

Detail explanation of how the solution come about can be found here:
https://github.com/AFNetworking/AFNetworking/issues/591#issuecomment-993
0763
Merge pull request #618 from lxcid/master

[Issue #591] Attempts to fix crash caused by incorrect calculation of range when reading data into buffer.
Merge pull request #617 from tewha/master

Document change in CHANGES