Restore support of URL for CSV

[chopraanmol1]

Summary

Fixes #378 #374 (Introduced in #368)

Benchmark

file_name = 'test/files/Bibelbund.csv'

MemoryProfiler.report{ Roo::Spreadsheet.open(file_name).tap{|x|(2..x.last_row).each{|i| x.row(i)}} }
puts Benchmark.measure{ Roo::Spreadsheet.open(file_name).tap{|x|(2..x.last_row).each{|i| x.row(i)}} }

Master

Total allocated: 39705265 bytes (561479 objects)
Total retained:  768 bytes (4 objects)

  0.300000   0.000000   0.300000 (  0.304877)

Modified:

Total allocated: 16952085 bytes (234487 objects)
Total retained:  768 bytes (4 objects)

  0.190000   0.000000   0.190000 (  0.181199)

[chopraanmol1]

@matiasgarcia can you verify if this PR solves your use case

[coveralls]

Coverage increased (+0.3%) to 94.079% when pulling e29ffe7 on chopraanmol1:restore_support_or_url_for_csv into 8d5ea7a on roo-rb:master.

[tgturner]

I will wait to see if @matiasgarcia can verify that this addresses his issue before merging.

[tgturner]

@chopraanmol1 Would you like to keep waiting to see if this is confirmed by the user? I'm ok with going ahead and merging if you are.

[chopraanmol1]

@tgturner lets go ahead with this. We can address additional cases (if any) in separate PR.