Cpymad

- update to MAD-X 5.06.00
- show empty tables as empty rather than raising exception (57)
- produce windows builds with msys2/mingw-w64 toolchain. No more dependency on
older MSVCRT dlls. Let's see if there will be any runtime errors from this.

- add ``limits`` parameter to ``Madx.match``
- try to download and build MAD-X in setup.py if it is not already available

Increase test coverage up to ``96%`` (from 75), and fix a few minor bugs
detected in the tests:

Command composition:
- handle composite ranges (``A/B``) in
- fix AttributeError when composing command with equality ``Constraint``
- fix incorrect output for STRING_ARRAY range parameters (MATCH)
- fix passing ``Range`` objects as ranges

Misc:
- fix table column names being ``bytes``, return as unicode ``str``
- fix the ``sectortable2`` method
- add ``Madx.options`` property that allows to view the current set of options
- remove unused helper method ``Sequence._parse_range``
- return the cloned element from ``Element.clone``

- add MAD-X specific metadata in cpymad.madx.metadata
- speedup Travis testing (using caches and docker containers)

- update to MAD-X 5.09.03

- command/element etc:
* retrieve information about commands from MAD-X ``defined_commands`` and
store in ``Command`` instances.
* use ``Command`` to improve command string generation and type-checks in
``util.mad_command`` (9)
* quote filename parameters when composing command string
* use deferred expressions (``:=``) whenever passing strings to
non-string parameters (11)
* subclass elements, beam from ``Command``
* support attribute access for table/mappings/commands/elements/beams etc
* allow case-insensitive access
* overload index-access in tables to retrieve rows
* implement ``Element.__delitem__`` by setting value to default
* return name for global elements too
* add ``Madx.base_types`` data variable that yields the base elements
* add ``Element.parent``/``base_type`` attributes
* more concise string representations
* strip -Proxy suffix from class names
* apply user defined row/column selections even when no output file is
specified

- installation:
* automatically use ``-lquadmath``
* add ``--static`` flag for setup script, use ``--shared`` by default
* no more need to link against PTC shared object separately
* finally provide some binary wheels for py 3.5 and 3.6 (32)

- raise cython language_level to 3
- require MAD-X 5.04.00