trace active_merchant vault store/unstore/update methods
support ruby 1.9+ public_instance_methods array of symbols

pre 1.9 ruby used array of strings, this fixed active_merchant
instrumentation for newer ruby versions
RUBY-1259 - VM Sampler records thread count.
Use MonotonicGCProfiler in the stats engine.
Inherit from sampler and adhere to the interface.
Include the vm sampler.
RUBY-1259 Subscribe the VM sampler to the transaction_finished event
RUBY-1259 Reset the transaction count on poll of the VM sampler
RUBY-1259 Add a stub_snapshot helper to VM sampler test
RUBY-1259 VM sampler records the GC runs metric
RUBY-1259 VM sampler records total_allocated_object metric
RUBY-1259 VM sampler records major/minor GC counts, heap metrics
RUBY-1259 Record VM cache invalidation metrics
RUBY-1259 Dry up VM sampler
RUBY-1259 Additional tests around partial data in VM sampler
RUBY-1259 Ensure VM samplmer records actual deltas
RUBY-1259 Constants for all VM metric names
Remove dead code in LocalEnvironment#check_for_mongrel
Add dispatcher detection for puma, update comments
RUBY-1272 Switch RUM insertion tests to cross_agent_tests fixtures

The new fixtures include test cases around insertion after the charset meta tag,
which will be fixed in the following commit.