Add rule to remove leading shell prompt literal $ (#996)

* Add rule to remove shell prompt literals $

Rule added to handle cases where the $ symbol is used in the command,
this usually happens when the command is copy pasted from a
documentation that includes the shell prompt symbol in the code blocks.

* Change files using black and flake8 style check

* Refactor tests and rule

- Refactor test for cleaner test tables
- Removed unnecessary requires_output=True option

thefuck/rules/remove_shell_prompt_literal.py

@@ -0,0 +1,22 @@
+"""Fixes error for commands containing the shell prompt symbol '$'.
+
+This usually happens when commands are copied from documentations
+including them in their code blocks.
+
+Example:
+> $ git clone https://github.com/nvbn/thefuck.git
+bash: $: command not found...
+"""
+
+import re
+
+
+def match(command):
+    return (
+        "$: command not found" in command.output
+        and re.search(r"^[\s]*\$ [\S]+", command.script) is not None
+    )
+
+
+def get_new_command(command):
+    return command.script.replace("$", "", 1).strip()