Rules: git remote add instead of set-url if remote does not exist

Tests: Added test for git_remote_seturl_add

Rules: renamed new rule with a more appropriate name

README: added new rule

Style: Formatting

New rule: corrected test name

Developed tests

thefuck/rules/git_remote_seturl_add.py

@@ -0,0 +1,14 @@
+from thefuck.utils import replace_argument
+from thefuck.specific.git import git_support
+
+
+@git_support
+def match(command):
+    return ('set-url' in command.script and 'fatal: No such remote' in command.stderr)
+
+
+def get_new_command(command):
+    return replace_argument(command.script, 'set-url', 'add')
+
+
+enabled_by_default = True