fix: fail2ban-regex with filter file failed

after merging #824, because test case missing;
test case for 'readexplicit' added;
@yarikoptic: please merge;
And `touch` does not read a file - it creates (and/or shares by name) an instance of ConfigReaderUnshared only...
If you try this new test without a fix in `fail2ban/client/configreader.py`:
```bash
bin/fail2ban-testcases ReaderExplicit
```
you will see
```
Fail2ban 0.9.0.dev test suite. Python 2.7.3 (default, Mar 14 2014, 11:57:14) [GCC 4.7.2]. Please wait...
.E...
======================================================================
ERROR: testFilterReaderExplicit (fail2ban.tests.clientreadertestcase.FilterReaderTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./fail2ban/tests/clientreadertestcase.py", line 341, in testFilterReaderExplicit
    self.assertEqual(filterReader.readexplicit(),
  File "./fail2ban/client/configreader.py", line 270, in readexplicit
    return SafeConfigParserWithIncludes.read(self, self._file)
TypeError: unbound method read() must be called with SafeConfigParserWithIncludes instance as first argument (got FilterReader instance instead)

----------------------------------------------------------------------
Ran 5 tests in 0.016s

FAILED (errors=1)
```