Add a script to add a TimeEntry

A script called 'spent' is added, this script allow the user to add
TimeEntries from the CLI.

The script allows the user to specify:
- issue_id: the issue id to add a time entry
- date: the date in format %Y-%m-%d
- comment: a comment for the time spent
- time: number of hours IE:0.4, 3
- activity: id of the activity, default is specifgy in the config file

Usage:
- python spent.py -i 4435 -t 0.1 -c 'Hell World' -a 10 -d 2013-11-13