Pull Request for Issue #719

[NehaDalmia]

Added the clause to check if a type is Scalar before iterating it.
fixes #719

[NehaDalmia]

The bug was arising as it was attempting to iterate over a non-iterable Symbol object. The Scalar struct declared is used to determine whether a given variable is iterable or not, if not we create a DisjointSet having just one element of the non iterable type. If it is iterable , we iterate over its members and the DisjointSet is created with these members.

[oxinabox]

I don't think this is the right solution.
Constructors for collections should not accept single elements.
They always should take iterators; the user should have to put the thing into a collection before hand.
Like:

julia> Set(:a)
ERROR: MethodError: no method matching length(::Symbol)

julia> Set([:a])
Set{Symbol} with 1 element:
  :a

We should find out why this is not throwing a MethodError and was instead infinitely recursing.

Also PR should have a test to prevent the bug occuring again in the future.