Added basic logging feature to understand how is configuration loaded

I've implemented some basic logging features when -d or --debug is added as an argument, it behaves like this:

``` bash

$ jrnl -d I\'ve just committed code on jrnl to enable debug mode with logging
DEBUG    jrnl.cli     Reading configuration from file /home/myuser/.jrnl_config
DEBUG    jrnl.util    Configuration file /home/myuser/.jrnl_config read correctly
DEBUG    jrnl.cli     Using configuration {u'default_hour': 9, u'linewrap': 79, u'encrypt': False, u'default_minute': 0, u'tagsymbols': u'@', u'editor': u'vi', u'timeformat': u'%Y-%m-%d %H:%M', u'highlight': True, u'journals': {u'default': u'/home/myuser/journal.txt'}}
DEBUG    jrnl.cli     Using journal default
DEBUG    jrnl.cli     Using journal path /home/myuser/journal.txt
DEBUG    jrnl.cli     Appending raw line "I've just committed code on jrnl to enable debug mode with logging" to journal "default"
[Entry added to default journal]
```

Probably there is a lot more work to do with the logger, but it is a start