Regula Falsi method for minimization added

Regula Falsi is another minimization method which combines features from the bisection method and the secant method.
NOTE: The output of the following example conforms with the one generated by the online solver at http://um.mendelu.cz/maw-html/index.php?lang=en&form=regula_falsi
Preview image of the output of the online solver:
![screenshot from 2014-02-26 00 54 24](https://f.cloud.github.com/assets/1975189/2261770/e1bae53e-9e52-11e3-91a8-53c919b8a400.png)

Example:
```
min=Minimization::RegulaFalsi.new(-1,5 , proc {|x| 4*(x)**2 + 8*(x) + 1})
min.iterate
puts min.log
```
generates the following output:
```
1
-0.875
5.0
-2.9375
141.0
5.875
143.9375
2
-0.7551020408163265
5.0
-2.760099958350687
141.0
5.755102040816326
143.76009995835068
3
-0.6446078431372549
5.0
-2.494785659361784
141.0
5.644607843137255
143.49478565936178
4
-0.546471268800617
5.0
-2.1772467599067116
141.0
5.546471268800617
143.17724675990672
5
-0.4621280028684116
5.0
-1.8427748588067063
141.0
5.462128002868412
142.8427748588067
6
-0.3916626106270523
5.0
-1.5197024827636265
141.0
5.391662610627052
142.51970248276362
7
-0.33417074871003283
5.0
-1.226685632506567
141.0
5.334170748710033
142.22668563250656
8
-0.2881642585096883
5.0
-0.9731595085477525
141.0
5.288164258509688
141.97315950854775
9
-0.25191636948090856
5.0
-0.7614835269975021
141.0
5.251916369480909
141.7614835269975
10
-0.2237052665703877
5.0
-0.5894659473977887
141.0
5.223705266570388
141.5894659473978

```