message: Fix typo in replace.h
  occurences -> occurrences
diff: @@ -27,7 +27,7 @@ namespace til
  }
  // Method Description:
  - // - This is a function for finding all occurences of a given string
  + // - This is a function for finding all occurrences of a given string
  // `needle` in a larger string `haystack`, and replacing them with the
  // string `replacement`.
  // - This find/replace is done in-place, leaving `haystack` modified as a result.
  @@ -50,7 +50,7 @@ namespace til
  }
  // Method Description:
  - // - This is a function for finding all occurences of a given string
  + // - This is a function for finding all occurrences of a given string
  // `needle` in a larger string `haystack`, and replacing them with the
  // string `replacement`.
  // - This find/replace is done on a copy of `haystack`, leaving `haystack`
  