applied minor refactoring

* removed pre-go1.8 internals
* started moving utilities to internal packages:
  * test helpers
  * debug logger
* code readability
  * wrapped complex statements as functions in analyzer, schema, fixer and mixin
  * refactored tests to remove unnecesary nested statement, favoring "require" over "assert"

NOTE: another refactoring with a focus on the most complex Flatten() functionality is coming.

Signed-off-by: Frederic BIDON <[email protected]>

Author: fredbi

.travis.yml

@@ -13,5 +13,5 @@ notifications:
   slack:
     secure: 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
 script:
-- gotestsum -f short-verbose -- -timeout=20m -coverprofile=coverage.txt -covermode=atomic -args -enable-long ./...
+- gotestsum -f short-verbose -- -timeout=20m -coverprofile=coverage.txt -covermode=atomic -coverpkg `echo $(go list ./...)|sed -E '1,$s/\s/,/'` -args -enable-long ./...
 - gotestsum -f short-verbose -- -race -timeout=20m  ./...