snmpset 16 bit integer support

original author: Marcin Jurczuk (@mrspock); commit broken up to make
future regression testing easier.
add mrspock to authors
optimise oidToString function to perform better

Before Optiomisation:
BenchmarkOidToString	 1000000	      1077 ns/op

After Optimisation:
BenchmarkOidToString	 5000000	       665 ns/op
mgenov to authors; helper_test license
fix boundary marshalInt16

original author: Marcin Jurczuk (@mrspock)
go fmt misc_test.go
set: OctetString, Integer, tests

Thanks to Marcin Jurczuk (@mrspock) for contributions.
Sets - updated readme, remove 1 oid limit.
Merge branch 'master' of https://github.com/soniah/gosnmp
Checkin of current auth code to fix a merge problem
Update changes to reflect new commits upstream
Fix username
Cleanup of marshal.go