Changed default n to 6 in gruntz.calculate_series
Fixed the infinite rescursion.
Added an extra condition that takes an expression with an order term
so that the expression could be added to another order term without
reaching maximum recusion depth.
Merge branch 'master' of https://github.com/sympy/sympy into series-expand
Fixed import typo
Fixed an error
Merge branch 'master' of https://github.com/sympy/sympy into series-expand
Used dummy symbol, fixed the test
Merge pull request #1798 from prasoon2211/series-expand

Fixed 'maximum recursion depth reached' issue for addition of Order term to another expression containing an order term.