Getting ready for CI: build automated test suite

Changes:
- examples, tests and tutorials from `PyDSTool/tests` moved to `examples`
- several tests converted/wrapped to use with `py.test` and moved to appropriate `tests` subdirectory (for example,  tests related to generators moved to `PyDSTool/Generator/tests` subdirectory)
- `setup.py` adjusted to use `py.test` in `python setup.py test` command
- tests from `PyDSTool/Toolbox/optimizers` included in test suite
- installation procedure and steps to run tests are described in ReadMe.md
- config file for Travis CI added

As a result:
- there are 238 tests in test suite
- though, 4 of them fails, marked for skipping and are to be fixed
- test coverage is about 33%
- [Travis CI runs](https://travis-ci.org/z2v/pydstool) test suite for two versions of Python (2.6, 2.7) and five pairs of `numpy`/`scipy` versions