Task add ... depends:XX ignores ranges

Hi,

It appears that the depends: attribute does not accept ranges, contrary to what is cited in the comment of the task file.

**Command run:** `task add foo depends:1-3`
**Expected behavior:** foo should depend on task 1, 2 and 3
**Actual behavior:** foo depends on task 1 only

**Output of the ```task diag``` command:**

>
> task 2.5.1
> Platform: Linux
>
> Compiler
> Version: 5.3.0
> Caps: +stdc +stdc_hosted +LP64 +c8 +i32 +l64 +vp64 +time_t64
> Compliance: C++11
>
> Build Features
> Built: Mar 9 2016 20:12:54
> CMake: 3.4.3
> libuuid: libuuid + uuid_unparse_lower
> libgnutls: 3.4.10
> Build type:
>
> Configuration
> File: /home/arthur/.taskrc (found), 1410 bytes, mode 100644
> Data: /home/arthur/.task (found), dir, mode 40755
> Locking: Enabled
> GC: Enabled
> Server:
> Trust: strict
> Certificate: , not readable, 0 bytes
> Key: , not readable, 0 bytes
> Ciphers: NORMAL
> Creds:
>
> Hooks
> System: Enabled
> Location: /home/arthur/.task/hooks
> (-none-)
>
> Tests
> $TERM: rxvt-unicode-256color (210x43)
> Dups: Scanned 189 tasks for duplicate UUIDs:
> No duplicates found
> Broken ref: Scanned 189 tasks for broken references:
> No broken references found

Thx for the good work :)