Note that the modifications include the fixes for issue #10 and issue #11
and should solve Debian bug 861091 and 861094.

This reverts commit f8088a59

According to the documentation of Python 3.5, the function fractions.gcd()
is deprecated and should be replaced by math.gcd().

So we modify the import of gcd() in lcm.py to import it from the math
module when possible, keeping the import from the fractions module if not
possible in order to keep the compatibility with older versions of Python.

As reported in Issue #2, many VisibleDeprecationWarnings were raised
when running the tests of ltfatpy with a recent version of numpy.

This is now solved by insuring that values used for indexes in numpy
arrays are integers, either by using integer division (//) where needed,
or by explicitely converting to integer type (changing np.func(X/2) to
int(np.func(X/2))), or by using int as the array dtype.