ENH: Have pivot and pivot_table take similar arguments

Right now, there is 
```
df.pivot(index=foo, columns=bar, values=baz)
```
and
```
df.pivot_table(rows=foo, cols=bar, values=baz)
```
Because of dirtyness in my data I occasionally have to go back and forth between the two forms (and use `df.pivot_table(..., aggfunc='count')` to see who had the bad data).  It would be nice if I didn't have to change the keyword arguments each time and one had an alias of the other.  It would also be easier to remember, especially in the trivial case of `cols` vs `columns`.  Finally, the two are related operations and having an option for consistent keyword parameters makes sense.

I could make a PR to solve this easy enough, if this is an enhancement you are interested in.  I'm not really sure what your stance is on redundant keyword arguments.