Removing the xccheckout file and adding it to .gitignore because it changes for each different developer.
Merge pull request #3 from jmacwhyte/master

Added struct comments
Merge branch 'master' into GetDataMessage

Conflicts:
	BitcoinSwift.xcodeproj/project.xcworkspace/xcshareddata/BitcoinSwift.xccheckout
Added GetData messages and tests.