Update Readme.md

Added the code markdown for NSOperation and BTTask
- Added pragma marks
- Fixed a typo "continuation" instead of "contination"
Removed the modifications on the xcheckout file
Minor typo fix
Switched to the newer Objective-C convention of “instancetype” rather than the less-DRY approach used previously.
Fix code examples (fixes #4)
Merge pull request #9 from chroman-forks/master

Minor typo fix
Merge pull request #7 from RuiAAPeres/master

Added a few pragma marks.
Update Readme.md
Merge pull request #10 from mrplants/master

Switched to the newer Objective-C convention of “instancetype”
Merge pull request #6 from RuiAAPeres/patch-1

Update Readme.md
Merge pull request #11 from travisjeffery/fix-code-examples

Fix code examples (fixes #4)
Fix method names with args
Merge pull request #12 from travisjeffery/fix-method-names-with-args

Fix method names with args
Update Readme.md
Minor typo in CONTRIBUTING.md
Merge pull request #13 from RuiAAPeres/patch-2

Update Readme.md
Updated Readme.md - ##Task Cancellation

Based on [comment](https://github.com/BoltsFramework/Bolts-iOS/issues/18#issuecomment-35766949) in #18
Fix minor typo in Readme.md (pod syntax)

Signed-off-by: Jai Govindani <jai@zodio.com>
Bolts with applinks prior to factoring out the web view resolver.