Fix heading level of 'Try' section

It was agreed to be '## Try:' but there were many files where it was
'### Try:'. This has been corrected.

2015/burton/README.md

@@ -20,7 +20,7 @@ or:
 Type in expressions on standard input.
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

2015/dogon/README.md

@@ -27,7 +27,7 @@ code](#alternate-code) below.
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./prog

2015/duble/README.md

@@ -15,7 +15,7 @@ echo Some text | ./prog
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

2015/endoh2/README.md

@@ -12,7 +12,7 @@ make
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

2015/endoh3/README.md

@@ -12,7 +12,7 @@ make
 ```
 
 
-### Try:
+## Try:
 
 To see the original [mullender](mullender.c) in action:
 

2015/endoh4/README.md

@@ -16,7 +16,7 @@ code](#alternate-code) below for details.
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

2015/hou/README.md

@@ -24,7 +24,7 @@ echo something | ./prog
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 echo "" | ./prog

2015/howe/README.md

@@ -17,7 +17,7 @@ below.
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

2015/mills1/README.md

@@ -12,7 +12,7 @@ make
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./prog

2015/mills2/README.md

@@ -23,7 +23,7 @@ For more detailed information see [2015 mills2 in bugs.md](/bugs.md#2015-mills2)
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

2015/muth/README.md

@@ -12,7 +12,7 @@ make -B [MACHINE=your_machine.h] [TAPE=your_tape.h] [X=[0|1|2|3|4|5|6|7|8|9]] [V
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

2015/schweikhardt/README.md

@@ -28,7 +28,7 @@ NOTE: although it's supposed to be a base 16 number nothing will stop you from
 doing something else. The author explains this in more details.
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

2015/yang/README.md

@@ -12,7 +12,7 @@ echo Some text | ./prog
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh