Add Travis continuous integration support

Adding configuration file and extending makefile to support
http://travis-ci.org.
avoid attempt to insert nil object into dictionary
Merge pull request #379 from sononum/master

avoid attempt to insert nil object into dictionary
Use the system-available quarantine string to get the quarantine metadata attribute.
Use some 10.10-specific APIs to remove the quarantine attribute.
Indenting code.
Xcode maintenance:
libxar is no longer weak-linked.
Removing undefined copy copies. Maybe they were icons?
Name the copy frameworks as "Copy Frameworks"
Merge pull request #388 from MaddTheSane/XcodeMaintanence

Xcode maintenance.
Better, forward-compatible way of looking up NSURLQuarantinePropertiesKey, as suggested by @jakepetroules
Minor fix.
Don't use new code if specifically targeting OS versions that have the new API.
Merge pull request #378 from grahammiln/travis

Add Travis continuous integration support
remove unnecessary return;
Merge pull request #387 from MaddTheSane/QuarantineVal

Quarantine removal
Xcode’s being weird
Xcode upgrade check harassment marker
Don't crash using CFPreferences when defaultsDomain is unknown
Added DSA verifier test
Add podspec.
Merge pull request #393 from xhacker/podspec

Add podspec