Added ability to set context name for SNMP variables
Initialize variable so we can detect missing snmpd correctly
Create BUILD directory during RPM build (required for SLES11SP2)
Throw out SuSE-specific python macros from RPM specfile

First of all, this module is noarch by definition. Second, SuSE macros won't be available on RHEL et al.
Added context argument to getRegistered and getContexts method
Work around unresolved dependencies bug in net-snmp 5.4.x libraries
Make comment about net-snmp 5.4.x workaround more verbose
Abstract certain functions from actual library for compatibility with net-snmp <5.6

From net-snmp 5.5 to 5.6, all code from libnetsnmphelpers.so got integrated into libnetsnmpagent.so. While this doesn't break C programs since ld-linux.so will take care of dynamically resolving referenced symbols, with ctypes all prototype definitions and functions calls always depend on a particular libX handle.

Therefore we now test using netsnmp_create_watcher_info whether that function is available in libnetsnmpagent and fall back to libnetsnmphelpers otherwise. The remaining code now uses libnsX to abstract from the actual library used.
Merge branch 'context' of https://github.com/kwirk/python-netsnmpagent
Fix example agent's working with SNMP contexts
Update README with credits
Distinguish libraries when errors in library loading occur