add .idea files to gitignore, add zsh note to installation docs (#329)

.gitignore

@@ -1,4 +1,5 @@
 .vscode/
+.idea/
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]

docs/installation.md

@@ -21,4 +21,10 @@ To install all modules needed for all integrations, run:
 
 ```
 pip install langchain[all]
+```
+
+Note that if you are using `zsh`, you'll need to quote square brackets when passing them as an argument to a command, for example:
+
+```
+pip install 'langchain[all]'
 ```