ENH: Bring Series.dot up to par with DataFrame.dot
If second argument is Series or DataFrame, ensures alignment of indices.
If second argument is some type of ndarray, just fall back to np.dot on the values.
This mirrors the behavior in DataFrame.dot

Includes unittest

@dieterv77 , by chance, I updated [CONTRIBUTING.md](https://github.com/pydata/pandas/blob/master/CONTRIBUTING.md) today with instructions
on getting Travis-CI working, can you try it out and let me know if it works out for you?
 @y-p I actually already configured it after i saw your instructions that you committed today.  I pushed an old local branch to my fork and it triggered a build on travis.  Any way that i can get it to trigger on this PR?  

thanks
 I have these aliases defined in .bashrc:

```
alias gca='git commit --amend'
alias gcac='gca -C HEAD'
```

so doing `gcac` gives the current branch a new hash without touching anything else.
if you then force push that to the PR branch, it should trigger a new build on travis for this PR.
 Looks like that worked.  thanks
 I just hit this and fixed with 66cbdc0.
fyi @dieterv77
