kwarg 'exact' in span, span_range and interval

[jadchaar]

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Description of Changes

Updated https://github.com/crsmithdev/arrow/pull/731 to latest master changes.

Closes: https://github.com/crsmithdev/arrow/issues/498

[codecov-commenter]

Codecov Report

Merging #817 into master will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #817   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9         9           
  Lines         1771      1785   +14     
  Branches       304       308    +4     
=========================================
+ Hits          1771      1785   +14     

Impacted Files	Coverage Δ
arrow/arrow.py	100.00% <100.00%> (ø)

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[systemcatch]

@jadchaar this was the bug we found, the last tuple ends up being wrong.

from datetime import datetime
import arrow

start = datetime(2013, 5, 5, 12, 30)
end = datetime(2013, 5, 5, 12, 40)

for r in arrow.Arrow.span_range('minute', start, end, exact=True):
    print(r)

(<Arrow [2013-05-05T12:30:00+00:00]>, <Arrow [2013-05-05T12:30:59.999999+00:00]>)
(<Arrow [2013-05-05T12:31:00+00:00]>, <Arrow [2013-05-05T12:31:59.999999+00:00]>)
(<Arrow [2013-05-05T12:32:00+00:00]>, <Arrow [2013-05-05T12:32:59.999999+00:00]>)
(<Arrow [2013-05-05T12:33:00+00:00]>, <Arrow [2013-05-05T12:33:59.999999+00:00]>)
(<Arrow [2013-05-05T12:34:00+00:00]>, <Arrow [2013-05-05T12:34:59.999999+00:00]>)
(<Arrow [2013-05-05T12:35:00+00:00]>, <Arrow [2013-05-05T12:35:59.999999+00:00]>)
(<Arrow [2013-05-05T12:36:00+00:00]>, <Arrow [2013-05-05T12:36:59.999999+00:00]>)
(<Arrow [2013-05-05T12:37:00+00:00]>, <Arrow [2013-05-05T12:37:59.999999+00:00]>)
(<Arrow [2013-05-05T12:38:00+00:00]>, <Arrow [2013-05-05T12:38:59.999999+00:00]>)
(<Arrow [2013-05-05T12:39:00+00:00]>, <Arrow [2013-05-05T12:39:59.999999+00:00]>)
(<Arrow [2013-05-05T12:40:00+00:00]>, <Arrow [2013-05-05T12:39:59.999999+00:00]>)

[jadchaar]

Closing this for now until we get a chance to take a closer look at the issue.