[docs] Improve the "introduction" page of the tutorial (issue 14097)

[ezio.melotti at gmail.com]

I added a few minor comments, otherwise the patch LGTM.


http://bugs.python.org/review/14097/diff/11998/Doc/tutorial/introduction.rst
File Doc/tutorial/introduction.rst (right):

http://bugs.python.org/review/14097/diff/11998/Doc/tutorial/introduction.rst#newcode68
Doc/tutorial/introduction.rst:68: remainders can be calculated with the
``%`` operator::
I would do s/, and remainders/. The remainder/
Also you could say "no matter what the types of the operands are".

http://bugs.python.org/review/14097/diff/11998/Doc/tutorial/introduction.rst#newcode70
Doc/tutorial/introduction.rst:70: >>> 17 / 3  # integer division returns
an int
Here you could say "# int / int -> int", and on the next line "int /
float -> float".
This emphasizes that the result depends on the input type, rather than
the names of the two types of divisions.

http://bugs.python.org/review/14097/diff/11998/Doc/tutorial/introduction.rst#newcode72
Doc/tutorial/introduction.rst:72: >>> 17 / 3.0 # classic division
returns a float
Two spaces before the #

http://bugs.python.org/review/14097/