Issue #26 Use pure python on compilation failure

'setup.py test' also uses SystemExit, with args[0] as False.
Detect and re-raise.

Add support for building without extension even when compiler
is functional, and set up extension-less travis builds.

Allow the compilation of the extension to fail, and switch
to pure python mode.

Another thing missed in #91

Target documentation for Python 3 usage

2 is dead, long live 3. Mainly turning print info a function
and urllib import fixes

Update README.rst for Pywikibot core

The new version ('core') is much more used and developed
than the previous one ('compat').

Force opening README.rst as utf-8 in Py3k

Causes issues if the locale is not set to utf-8

Tests were not correctly testing the situations without a table close.
Fixed tests and then fixed tokenizers for failing tests. Also refactored
pytokenizer to more closely match the ctokenizer by only holding the
`_parse` methods in the try blocks and no other code.

One-line fix

Add some table tests to increase coverage. Also reorder some tests.

Python 3.4 compiles C extensions with the
`-Werror=declaration-after-statement` flag that enforces C90 more
strictly than previous versions. Move all statements after declarations
to make sure this extension builds on 3.4.

For wiki syntax tables, add `wiki_style_separator` as an attribute
for the Tag node. Also reorder `closing_wiki_markup` property and tests
to match its place in the constructor.