API: Include the region of the match, not just the position

`MatchResult.region` contains all the information that `position` does,
plus indicating the size of the matched area.  This can be useful for OCR
which takes a region to read from.  So with this change it's easy and
convenient to read the text next to a matching icon for instance:

    text = ocr(region=wait_for_match('icon.png').region.extend(right=200))

This changes the arguments `MatchResult` constructor.  This would be a
backwards compatibility break but `MatchResult`s should only be being
created by core stbt code and not by user code.  Still this is something
to watch out for.

Users can still write `pos = match_result.position` so the user facing API
has not been broken.
Fix display of `Region` documentation in web page

Unlike the man page (generated by rst2man), the web version at
http://stb-tester.com/stbt.html is generated by pandoc. Pandoc
requires that each line in an indented code block be indented
at least as much as the first line.
Use pylint 1.1.0 on Travis CI

This should minimise differences between `make check` on developer's
machines and Travis CI. 1.1.0 is the same version as in Ubuntu 14.04.

Pylint 1.x knows about namedtuple members[1] so we no longer have to
ignore E1101 errors regarding stbt.Position, stbt._Rect, stbt._Size,
and stbt.Region.

[1] http://www.logilab.org/revision/148201
Ignore pylint error on Travis CI

The error was:

    stbt.py:1680: [E1120(no-value-for-parameter), Display.teardown] No
    value for argument 'self' in unbound method call

referring to `Gst.Event.new_eos()`, which is a static method, but I
guess that pylint doesn't know that.

There are 2 very odd things about this:

1. This error doesn't happen on my own machine running the same version
   of pylint (1.1.0).
2. extra/pylint.conf says `ignored-classes=Event`, so pylint should be
   ignoring any errors related to `Event`.

Note that E1120 exists on pylint 0.28, so users of that version
shouldn't get an error due to the newly-introduced "pylint: disable"
annotation.

Other things I tried before settling on this solution:

* Upgrading Travis CI to pylint 1.2.0 (same error happens; I decided to
  stay on 1.1.0 because that's the version on Ubuntu 14.04).
* Changing extra/pylint.conf to say `ignored-classed=Gst.Event` (same
  error happens).
Merge pull request #179 from wmanley/api-matchresult-region

API: Include the region of the match, not just the position