Add .editorconfig file and fix whitespaces in existing files. (#4)

.editorconfig

@@ -0,0 +1,14 @@
+# EditorConfig helps developers define and maintain consistent
+# coding styles between different editors and IDEs
+# http://editorconfig.org
+
+root = true
+
+[*.rs]
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+indent_style = space
+indent_size = 4
+max_line_length = 120