Move Mathematical Thinking to extra courses

Closes ossu#420

README.md

@@ -317,7 +317,6 @@ Courses | Duration | Effort | Prerequisites
 ### Advanced math
 
 **Topics covered**:
-`real analysis`
 `parametric equations`
 `polar coordinate systems`
 `multivariable integrals`
@@ -327,7 +326,6 @@ Courses | Duration | Effort | Prerequisites
 
 Courses | Duration | Effort | Prerequisites
 :-- | :--: | :--: | :--:
-[Introduction to Mathematical Thinking](https://www.coursera.org/learn/mathematical-thinking) | 10 weeks | 10 hours/week | pre-calculus
 [Calculus: Parametric Equations and Polar Coordinates](https://ocw.mit.edu/courses/mathematics/18-01sc-single-variable-calculus-fall-2010/unit-4-techniques-of-integration/part-c-parametric-equations-and-polar-coordinates/) | - | - | single-variable calculus (Calculus Two)
 [Multivariable Calculus](https://ocw.mit.edu/courses/mathematics/18-02sc-multivariable-calculus-fall-2010/index.htm) | 13 weeks | 12 hours/week | Parametric Equations and Polar Coordinates
 [Introduction to Probability - The Science of Uncertainty](https://www.edx.org/course/introduction-probability-science-mitx-6-041x-2) | 18 weeks | 12 hours/week | Multivariable Calculus

extras/courses.md

@@ -24,6 +24,7 @@ Courses | Duration | Effort
 Courses | Duration | Effort
 :-- | :--: | :--:
 [Effective Thinking Through Mathematics](https://www.edx.org/course/effective-thinking-through-mathematics-utaustinx-ut-9-01x-0) | 4 weeks | 2 hours/week | none
+[Introduction to Mathematical Thinking](https://www.coursera.org/learn/mathematical-thinking) | 10 weeks | 10 hours/week
 [Introduction to Probability and Data](https://www.coursera.org/learn/probability-intro)| - | -
 [Linear Algebra (Strang)](https://ocw.mit.edu/courses/mathematics/18-06-linear-algebra-spring-2010/index.htm) | - | -