Improve INFO log when using the --info optional argument
Move filter parsing to a standalone method in Merge command

The include and exclude filter are now parsed and stored in a dictionary
with 3 keys: label (default), pr & user. Each filter can be attributed to the
corresponding key using the key:value syntax in the command line.
Modify filter check logic to account for new filter types

For each filter (include or exclude), labels, user and pull request number
are successively tested against the values of the filter dictionary. If the
intersection is not null, it is logged in DEBUG.
Add description of the new filter keys in the parser help
Do not propagate filters PR numbers across submodules
Use mox for writing mocked tests of Merge

With @sbesson's changes, it now should be
fairly straight-forward to write mocked
tests. This is currently done using mox.
Like Sandbox.py, Mocks.py provides a base
class which should be used by all mocked
tests.
Add missing test/Mock.py
Pass filters directly to run_filter() and add action optional argument
Add filtering unit tests
Remove get_user() get_organization() function overloading

These overloaded functions (for mox testins) do break the instantiation of
real repositories.
Replace lstrip by replace to fix bug

Example of filter that was not working properly with lstrip(): "user:sbesson".
In this case, s.lstrip(key + ":") will also strip the first "s" character.
Add default optional argument to control the whitelisting mode

Define 4 default modes: none, mine, org and alls. Allow better granularity and
potentially any possibility when combined with include/exclude filters.
Re-overload get_user() and get_organization() method for mox tests
Rename dev_requirement to let the Travis build pass
Add -D optional argument to specify default mode

Improve INFO log message to specify default mode
Add default mode and use single character options in commit message
Force include/exclude filter arguments to be specified multiple times

Command for including/excluding multiple filters should be now formatted as:
scc merge master -Dnone -Iuser:user1 -Iuser:user2 -Itest -Ilabel:test2 -Ipr:42 -Ipr:23 -Epr:39
Fix commit id to be consistent with recent optional arguments changes
Merge pull request #39 from sbesson/merge_filters

Merge filters