Add sudoku support

[pranavprakash20]

Adding support for solving sudoku puzzles.

Sample input : 3 0 6 5 0 8 4 0 0 5 2 0 0 0 0 0 0 0 0 8 7 0 0 0 0 3 1 0 0 3 0 1 0 0 8 0 9 0 0 8 6 3 0 0 5 0 5 0 0 9 0 6 0 0 1 3 0 0 0 0 2 5 0 0 0 0 0 0 0 0 7 4 0 0 5 2 0 6 3 0 0 ~> Hi, what can I do for you? sudoku /home/ws/pranav/sudoku_input 3 1 6 5 2 8 4 9 7 5 2 1 3 4 7 8 6 9 2 8 7 6 5 4 9 3 1 6 4 3 9 1 5 7 8 2 9 7 2 8 6 3 1 4 5 7 5 8 4 9 1 6 2 3 1 3 4 7 8 9 2 5 6 8 6 9 1 3 2 5 7 4 4 9 5 2 7 6 3 1 8

[pnhofmann]

Really nice! Like it.

Just some smaller notices (parsing a file is always tricky!):

Crashes if for example one line has leading zeros or contains illegal characters:

Some error occurred, please open an issue on github!
Here is error:

Traceback (most recent call last):
  File "/home/phil/git/Jarvis/jarviscli/CmdInterpreter.py", line 286, in try_do
    do(self, s)
  File "/home/phil/git/Jarvis/jarviscli/plugin.py", line 208, in run
    self._backend[0](jarvis.get_api(), s)
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 40, in __call__
    self.sudoku.append([int(i) for i in line.split(" ")])
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 40, in <listcomp>
    self.sudoku.append([int(i) for i in line.split(" ")])
ValueError: invalid literal for int() with base 10: '\n'

Crahses if numbers are missing:

Some error occurred, please open an issue on github!
Here is error:

Traceback (most recent call last):
  File "/home/phil/git/Jarvis/jarviscli/CmdInterpreter.py", line 286, in try_do
    do(self, s)
  File "/home/phil/git/Jarvis/jarviscli/plugin.py", line 208, in run
    self._backend[0](jarvis.get_api(), s)
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 43, in __call__
    if self.solve():
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 59, in solve
    return self.solve(row, col + 1)
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 68, in solve
    if self.solve(row, col + 1):
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 59, in solve
    return self.solve(row, col + 1)
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 59, in solve
    return self.solve(row, col + 1)
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 68, in solve
    if self.solve(row, col + 1):
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 59, in solve
    return self.solve(row, col + 1)
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 59, in solve
    return self.solve(row, col + 1)
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 68, in solve
    if self.solve(row, col + 1):
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 63, in solve
    if self._is_valid(row, col, num):
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 93, in _is_valid
    if self.sudoku[i][col] == num:
IndexError: list index out of range

Crashes if file does not exists or no parameter given

~> Hi, what can I do for you?
sudoku
Some error occurred, please open an issue on github!
Here is error:

Traceback (most recent call last):
  File "/home/phil/git/Jarvis/jarviscli/CmdInterpreter.py", line 286, in try_do
    do(self, s)
  File "/home/phil/git/Jarvis/jarviscli/plugin.py", line 208, in run
    self._backend[0](jarvis.get_api(), s)
  File "/home/phil/git/Jarvis/jarviscli/plugins/sodoku.py", line 37, in __call__
    with open(sudoku, 'r') as fp:
FileNotFoundError: [Errno 2] No such file or directory: ''

(Maybe add a try-except for above issues and minimum print "invalid input file")

And causes infinity loop, if sudoku is unsolvable (e.g. input file contains twice same number in one line)