ENH : Added draft of integrate_ROI
TST : added some tests for integrate_ROI
MNT: Added __init__.py file to the nsls2.io package and fixed setup.py to
include the nsls2.io package
initiate fitting wrapper for generic fitting
DEV: Updated spectroscopy.integrate_ROI based on comments in grp meeting

1) made function more general by removing references to energy
   replaced energy references with x-value references.
   energy --> x_value_array
   e_min --> x_min
   e_max --> x_max
2) added value check on x_value_array to make sure that the array
   increases in value, and if the array decreases in value, then
   the array is flipped to correct orientation. This check is followed
   by confirmation that values in x_value_array are equally spaced
3) updated documentation
BUG: Corrected test function name typos

Test functions for integrate_ROI were spelled intagrate.
Corrected spelling for both integrate_ROI test functions.
DEV: spectroscopy.py - Fixed Caswell's comments

1) Added array reversal for both counts and x_value_array in the event that
   the arrays are input running highest to lowest value in the independant
   variable array.
2) Removed the x_value_array spacing test which also resolves Tom's comment
   about not using exact float arithmetic for testing.
3) Added a value check on the x_min and x_max values so that in the event
   that the user assigns the maximum bounds to x_min and minimum bounds
   to x_max, the code corrects for this error automatically without
   raising an exception.
DEV: Added unittests for mods to spectroscopy.py

1) Added 2 tests to test_integrate_ROI_compute()
   a) Evaluate case where x_value_array, and compute are entered
      with monotonically decreasing x_array values
   b) Evalute case where all input parameters are entered "backwards"
2) Commented out unit test where all x_min and x_max values are flipped
   since a correction for this case has been added to the code resulting
   in this case NOT resulting in an exception error.
add target function for test
add simple test
rewrite leastsq fit as a single function
add parameters class for fitting data
add args=() as input for fitting engine
DEV: Finished updating integrate_ROI per Tom's github comments

Finished updating ValueError messages using .format()
Removed auto-correction of max/min boundaries so that ValueError
exception is raised instead.
DEV: Added test case for reversed x_value_array and counts input

The test verifies that if both the 'x_value_array' and 'counts' data sets
are input in reversed order (so that the values are decreasing monotonically)
then both arrays are flipped so that the independent variable values meet
the "monotonically increasing" required condition.
In the event that this reversal occurs, a print statement is generated in
order to notify the user that this reversal has occurred.
test lmfit fitting class
add model folder with all functions for fitting
remove parameters, previously used for storing fitting inputs
update on background.py: license, docstring, input
add space to math equation, remove unused binning parameters