bisection method for minimization added

I have added the bisection method for minimization.
Below is the output log for first 15 iterations compared to the results given on the wikipedia page (https://en.wikipedia.org/wiki/Bisection_method#Example:_Finding_the_root_of_a_polynomial). 
The results match.
NOTE:
The wikipedia page mentions the first iteration in the state before the iteration, but my log mentions the state of the interval after the iteration, because that was the convention followed in the previously implemented Golden Section Method. Also, the ```Cn``` mentioned on the wikipedia page is equivalent to ```bx``` in my code(again following the convention of the previously written code)

PS: I will come up with a test suite for all methods soon.
Thanks
```
1 #iteration number
1.5 #lower limit of interval after first iteration, equivalent to wikipedia's interval lower limit in iteration 2
2.0 #upper limit of interval after first iteration, equivalent to wikipedia's interval lower limit in iteration 2
-0.125 # f(ax)
4.0 # f(cx) NOTE that f(cn) on wiki page is equal to f(bx) in the code
0.5 # (ax-cx).abs
4.125 # (f(ax)-f(cx)).abs
2
1.5
1.75
-0.125
1.609375
0.25
1.734375
3
1.5
1.625
-0.125
0.666015625
0.125
0.791015625
4
1.5
1.5625
-0.125
0.252197265625
0.0625
0.377197265625
5
1.5
1.53125
-0.125
0.059112548828125
0.03125
0.184112548828125
6
1.515625
1.53125
-0.034053802490234375
0.059112548828125
0.015625
0.09316635131835938
7
1.515625
1.5234375
-0.034053802490234375
0.012250423431396484
0.0078125
0.04630422592163086
8
1.51953125
1.5234375
-0.010971248149871826
0.012250423431396484
0.00390625
0.02322167158126831
9
1.51953125
1.521484375
-0.010971248149871826
0.0006221756339073181
0.001953125
0.011593423783779144
10
1.5205078125
1.521484375
-0.005178886465728283
0.0006221756339073181
0.0009765625
0.005801062099635601
11
1.52099609375
1.521484375
-0.002279443317092955
0.0006221756339073181
0.00048828125
0.0029016189510002732
12
1.521240234375
1.521484375
-0.0008289058605441824
0.0006221756339073181
0.000244140625
0.0014510814944515005
13
1.5213623046875
1.521484375
-0.0001034331235132413
0.0006221756339073181
0.0001220703125
0.0007256087574205594
14
1.5213623046875
1.52142333984375
-0.0001034331235132413
0.0002593542519662151
6.103515625e-05
0.0003627873754794564
15
1.5213623046875
1.521392822265625
-0.0001034331235132413
7.795631350404619e-05
3.0517578125e-05
0.0001813894370172875
```