Christopherngutierrez/test context parse results

[christopherngutierrez]

Proposed changes

Changes:

• kerngen/high_parser/parser.py: added _get_context_from_commands_list static method to verify that ParseResults._commands contains exactly one Context.
• kerngen/tests/test_kerngen.py: contains two additional test to verify that a "LookupError" is raised if multiple Context or no Context is found in ParseResult._commands.
• pytest.ini: points to the source code directory. Fixes issue with imports on tests.

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[christopherngutierrez]

Removed README.MD from pull request, per @faberga suggestion.

[jobottle]

LGTM