tests: simple JSON test

[jirikuncar]

• Adds test for JSON/JSONB fields. (closes types: possible to support both JSON/JSONB #19)

Signed-off-by: Jiri Kuncar jiri.kuncar@cern.ch

[tiborsimko]

Please see a couple of Travis CI issues with development dependencies:

> raise exc.UnsupportedCompilationError(visitor, cls)

E CompileError: (in table 'test_json', column 'js'): Compiler
  <sqlalchemy.dialects.sqlite.base.SQLiteTypeCompiler object at 0x7f6f82efee50>
  can't render element of type <class 'sqlalchemy.sql.sqltypes.JSON'>

[jirikuncar]

We might still need to fallback to SQLAlchemy-Utils. 😞

[jirikuncar]

We need to wait for SQLAlchemy 1.1.