cleanup after SeparateJvmsExecutor properly

SeparateJvmsExecutor contains a laziness bug which causes it to execute
 #cleanupAfter before the benchmarks are run.
Merge pull request #40 from danburkert/master

cleanup after SeparateJvmsExecutor properly
Add defaultConfig
Use mkdirs() instead of mkdir()
Avoid rebuilding context so much
Fix a typo
Merge pull request #44 from alexeyr/topic/default-config

Add defaultConfig
Merge pull request #45 from alexeyr/issue/41

Use mkdirs() instead of mkdir()
Made configuration type-safe
Merge pull request #46 from alexeyr/topic/type-safe-keys

Made configuration type-safe
Prevent calling apply on keys without a default
Setting verbose by default, adding the silent option.
Fixing conflicts.
Create README.md
Deprecated Aggregator.complete
Made Aggregator.data non-optional
Merge pull request #49 from alexeyr/issue/30

Issue/30
Extracted common code
Added feature warnings
Removed reflective calls