Add "build" action for the schemes
Update OS X test so they are buildable

- Set the correct OS X SDK Root
- Remove UIKit framework for OS X tests
Reintroduce the travis-ci badge
Prevent the -Wformat warning when using NSUInteger in the tests

    warning: values of type 'NSUInteger' should not be used as format arguments;
    add an explicit cast to 'unsigned long' instead [-Wformat]
Removed empty, unused else clause.
Merge pull request #1600 from lukabratos/master

Removed empty, unused else clause.
[Issue #1566] Fixing NSURLSession subspec
Bumping version to 2.0.3
Removed two unused empty else clauses.
fixes -Wsign-conversion on 64bit by changing offset to u_int64_t and return an unsigned long long value from output stream offset.
fixes -Wconversion when encoding CGFloat as float in 64bit mode. Encode NSNumber instead of float.
force progress upload, by using original request content-length
use consts not hardcoded values
Add a test that a stream failure for an operation is handled

Closes #1538
Add a CONTRIBUTING page to take questions to SO
Merge pull request #1613 from kylef/contributing

Add a CONTRIBUTING page to take questions to SO
Typo in comments
Fixes a bug in appending part file with a URL

-[NSFileManager attributesOfItemAtPath:error:] may fail and the error wasn't
being handled. The body content length would be 0 if that is the case, and this
would result in the content length being incorrect. Let's just throw the error
back instead of silently handling this issue.
You should use the suggested filename and not a temporary filename

Closes #1635
Fixes a couple of bugs for when a task becomes a download task

If a task becomes a download task. None of the old delegate methods for
the old task will get called. This means it wont remove the observer
and it will not delete the delegate.

We never setup the new task with observing and it’s delegate either.