travis: known_failures: add test__issue6.py

It often fails with:

master ~/work/gevent $ python greentest/test__issue6.py
Traceback (most recent call last):
  File "greentest/test__issue6.py", line 11, in <module>
    assert err == '', (out, err, code)
AssertionError: ('11 chars.\n', 'Unhandled exception in thread started by \nsys.excepthook is missing\nlost sys.stderr\n', 0)
drop support for Python 2.5
set version to 1.1dev
pep8 fixes
use as-syntax in except clauses #38
testrunner.py: fix syntax on py3
fix spurious failures in test__socket_dns6.py
replace "ex = sys.exc_info()[1]" with "as ex" #38
remove unused imports
pyflakes fixes
cythonpp.py: drop support for python2.5
disable tests in test_httpserver failing on 2.6

only on travis:

test_authorization (__main__.CGIHTTPServerTestCase) ... Traceback (most recent call last):
    File "/usr/lib/python2.6/CGIHTTPServer.py", line 255, in run_cgi
      os.execve(scriptfile, args, os.environ)
  OSError: [Errno 13] Permission denied
  FAIL
  test_headers_and_content (__main__.CGIHTTPServerTestCase) ... Traceback (most recent call last):
    File "/usr/lib/python2.6/CGIHTTPServer.py", line 255, in run_cgi
      os.execve(scriptfile, args, os.environ)
  OSError: [Errno 13] Permission denied
  FAIL
  test_invaliduri (__main__.CGIHTTPServerTestCase) ... ok
  test_post (__main__.CGIHTTPServerTestCase) ... Traceback (most recent call last):
    File "/usr/lib/python2.6/CGIHTTPServer.py", line 255, in run_cgi
      os.execve(scriptfile, args, os.environ)
  OSError: [Errno 13] Permission denied
  FAIL

  ======================================================================
  FAIL: test_get (__main__.SimpleHTTPServerTestCase)
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "test_httpservers.py", line 242, in test_get
    File "test_httpservers.py", line 218, in check_status_and_reason
  AssertionError: 200 != 404

  ======================================================================
  FAIL: test_authorization (__main__.CGIHTTPServerTestCase)
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "test_httpservers.py", line 349, in test_authorization
  AssertionError: ('Hello World\n', 'text/html', 200) != ("Exception happened during processing of request from ('127.0.0.1', 60525)\n----------------------------------------\n", None, 200)

  ======================================================================
  FAIL: test_headers_and_content (__main__.CGIHTTPServerTestCase)
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "test_httpservers.py", line 330, in test_headers_and_content
  AssertionError: ('Hello World\n', 'text/html', 200) != ("Exception happened during processing of request from ('127.0.0.1', 38970)\n----------------------------------------\n", None, 200)

  ======================================================================
  FAIL: test_post (__main__.CGIHTTPServerTestCase)
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "test_httpservers.py", line 337, in test_post
  AssertionError: "Exception happened during processing of request from ('127.0.0.1', 45146)\n----------------------------------------\n" != '1, python, 123456\n'
new travis build

- do pep8 and pyflakes checks
- do not tests examples with dependencies (psycopg2_pool.py, web.py, geventsendfile.py)
- do check -dbg build
- install cython from ppa
- drop 2.5, add 3.3 (currently fails)

new make commands:
 - make whitespace
 - make pep8
 - make pyflakes
 - make lint       # runs all of the above
 - make travis     # runs on travis

The linters are run first to abort broken builds early.

Removed --full option to testrunner.py, it is no longer needed.
Merge pull request #343 from surfly/travis

drop support for 2.5; improve travis; use py2.6+ syntax