Fix some arithmetical errors.
Use correct assertions on tests.
Fix typo
Merge pull request #445 from ovr/cont_typo

Fix typo
Merge pull request #441 from rodrigorm/sigmoid-error

Fix some arithmetical errors
Fix string constants escaping, IssetOperator with variables
Merge pull request #456 from ovr/serebro_fixes

Fix string constants escaping, IssetOperator with variables
Composer, compile json-c before install