BearRunner: Codestyle issues
BearCollector: Correct documentation
BearCollector: Default to no bears instead of all

This makes more sense as described in:
https://github.com/sils1297/coala/issues/128
TestHelper: Use system independent tempdir

Usage if tempfile.gettempdir() should be preferred over /tmp for
platform independency.
FileCollectorTest: Test consecutive invocations

This makes the test more thorough while increasing branch coverage.
default_coafile: Add current directories

This simplifies the coafile for many users so they can use Bears and
files from the current directory right ahead.
Section: other -> other_section

This makes the potentially raised TypeError more consistent with the
other messages we use because we don't need single quotes around the
parameter name for the sentence to not sound grammatically stupid.
doc: Update autogenerated documentation
Update po template
BearCollectorTest: Remove unneeded variable
TestHelper: Use coverage3

Since we are dependent on python3, we need to use the coverage3
binary/symlink on some distribution so the tests don't get executed with
python2.
Setting: Handle absolute paths
FileCollectorTest: Remove unneeded variable
BearCollectorTest: Dont break strings senselessly
BearCollector: Treat regex's the right way

Previously we collected every bear where the beginning of the bear name
matched the regex. We now match the whole string.
default_coafile: Add missing values

All these values are needed to operate coala without any IndexError
exceptions.
processes: Add SectionExecutor
processes: Add SectionExecutorTest