Test improvements

[cgrigis]

• The automated CI handled by .travis.yml appears to only perform formatting, linting and coverage checks, but does not execute tests.
• The tests for GenerateLoadingOntologyScript() and GenerateLoadingDataScript() (for both genomic and i2b2) only seem to ensure scripts can be generated, but don't check their correctness.
• The tests for packages identifiers, loadergenomic amd loaderi2b2 are located in a *_test package (i.e. identifiers_test, etc.), which forces many symbols in the tested packages to be unnecessarily public in order to be accessible. This is generally used for black-box tests, whereas for white-box tests, they should be in the same package as the tested code (and the symbols private).
• Test values in identifiers_test could be simplified by using 0b... binary literals in Go.