Add membership_validator config option, default to detect
Add Detect membership validation strategy

Detects ActiveDirectory capabilities, defaults to Recursive.
Move strategies map to GitHub::Ldap::MembershipValidators
Update required capability OID to match 2008 R2 v61
Proactively handle capapbility query errors, instrument
Fix detect_strategy doco
Ensure detect_strategy returns the strategy class
s/if/whether/
Move capabilities lookup to GitHub::Ldap
Only instrument when we query for capabilities
Server returns supportedCapabilities
Test Detect meta-strategy
fix typo
add test for validator detection
add script/changelog

see https://github.com/jch/release-scripts
add a changelog
bump version to 1.4.0
add release scripts
document how to release
Merge remote-tracking branch 'origin/master' into default-membership-validator