Fix broken links in README

Presently, the links pointed to by "GCC error compatibility" and
"CheckStyle compatible XML output" are broken due to improper
way of referring files. This change fixes those links.

Also, this commit removes some trailing whitespaces in README.

README.md

@@ -14,7 +14,7 @@ The goals of ShellCheck are
 
   - To point out subtle caveats, corner cases and pitfalls that may cause an
     advanced user's otherwise working script to fail under future circumstances.
-    
+
 See [the gallery of bad code](README.md#user-content-gallery-of-bad-code) for examples of what ShellCheck can help you identify!
 
 
@@ -48,13 +48,13 @@ You can see ShellCheck suggestions directly in a variety of editors.
 
 * Atom, through [Linter](https://github.com/AtomLinter/linter-shellcheck).
 
-* Most other editors, through [GCC error compatibility](blob/master/shellcheck.1.md#user-content-formats).
+* Most other editors, through [GCC error compatibility](shellcheck.1.md#user-content-formats).
 
 
 #### In your build or test suites
 While ShellCheck is mostly intended for interactive use, it can easily be added to builds or test suites.
 
-Use ShellCheck's exit code, or it's [CheckStyle compatible XML output](blob/master/shellcheck.1.md#user-content-formats). There's also a simple JSON output format for easy integration.
+Use ShellCheck's exit code, or it's [CheckStyle compatible XML output](shellcheck.1.md#user-content-formats). There's also a simple JSON output format for easy integration.
 
 
 ## Installing
@@ -174,7 +174,7 @@ ShellCheck can recognize many types of incorrect test statements.
     [[ -e *.mpg ]]                    # Existence checks of globs
     [[ $foo==0 ]]                     # Always true due to missing spaces
     [[ -n "$foo " ]]                  # Always true due to literals
-    [[ $foo =~ "fo+" ]]               # Quoted regex in =~ 
+    [[ $foo =~ "fo+" ]]               # Quoted regex in =~
     [ foo =~ re ]                     # Unsupported [ ] operators
     [ $1 -eq "shellcheck" ]           # Numerical comparison of strings
     [ $n && $m ]                      # && in [ .. ]
@@ -219,7 +219,7 @@ ShellCheck can make suggestions to improve style:
     [[ -z $(find /tmp | grep mpg) ]]  # Use grep -q instead
     a >> log; b >> log; c >> log      # Use a redirection block instead
     echo "The time is `date`"         # Use $() instead
-    cd dir; process *; cd ..;         # Use subshells instead 
+    cd dir; process *; cd ..;         # Use subshells instead
     echo $[1+2]                       # Use standard $((..)) instead of old $[]
     echo $(($RANDOM % 6))             # Don't use $ on variables in $((..))
     echo "$(date)"                    # Useless use of echo
@@ -265,7 +265,7 @@ ShellCheck will warn when using features not supported by the shebang. For examp
     foo-bar() { ..; }                # Undefined/unsupported function name
     [ $UID = 0 ]                     # Variable undefined in dash/sh
     local var=value                  # local is undefined in sh
-    
+
 
 #### Miscellaneous