`load` should be used to initialize externed constants

Fixes #142
Add missing line in ZXQRCodeReader

Fixes #149
In example app, make sure ZXImage isn't immediately released

Fixes #146
Typo Correction for readme.md

Typo correction for Installation instructions. (mamager => manager)
Merge pull request #157 from rbparson/patch-1

Typo Correction for readme.md
[Issue #153] Fix typo in ZXITFWriter
[Issue #162] Remove description property from ZXCalendarParsedResult
Link XCTest to unit test target
[Issue #155] Convert CFStringEncoding to NSStringEncoding
[Issue #156] Use height and width when encoding DataMatrix
[Issue #159] Allow on and off colors to be set in ZXImage
Version bump: 3.0.2
Fix implicit boolean conversion warnings
LastUpgradeVersion set to 0600
Version bump: 3.0.3
Merge commit 'befbef7e585342734846a04bf25e6749d995a85d'