Fix Swift and JavaScript code imports. (#208)

* Use lang:"javascript" instead of lang:"js" in monte_carlo.md to resolve warnings.

* Fix Swift import in monte_carlo.md.

Author: june128

chapters/monte_carlo/monte_carlo.md

@@ -44,7 +44,7 @@ each point is tested to see whether it's in the circle or not:
 {% sample lang="c" %}
 [import:7-9, lang:"c_cpp"](code/c/monte_carlo.c)
 {% sample lang="js" %}
-[import:2-6, lang:"js"](code/js/monte_carlo.js)
+[import:2-6, lang:"javascript"](code/js/monte_carlo.js)
 {% sample lang="hs" %}
 [import:7-7, lang:"haskell"](code/haskell/monteCarlo.hs)
 {% sample lang="rs" %}
@@ -99,7 +99,7 @@ Feel free to submit your version via pull request, and thanks for reading!
 [import, lang:"c_cpp"](code/c/monte_carlo.c)
 {% sample lang="js" %}
 ### Javascript
-[import, lang:"js"](code/js/monte_carlo.js)
+[import, lang:"javascript"](code/js/monte_carlo.js)
 {% sample lang="hs" %}
 ### Haskell
 [import, lang:"haskell"](code/haskell/monteCarlo.hs)
@@ -117,7 +117,7 @@ Feel free to submit your version via pull request, and thanks for reading!
 [import, lang:"java"](code/java/MonteCarlo.java)
 {% sample lang="swift" %}
 ### Swift
-[import, lang:"swift"](code/java/monte_carlo.swift)
+[import, lang:"swift"](code/swift/monte_carlo.swift)
 {% endmethod %}