Updating podspec to version 2.4.3
Converts enum typedefs to NS_ENUM or NS_OPTIONS as appropriate

Without this, they cannot be inferred by/using Swift.

Signed-off-by: Daniel Thorpe <danthorpe@me.com>
Merge branch 'master' of https://github.com/danthorpe/YapDatabase into danthorpe-master
Updating code to match new NS_OPTIONS syntax.