📄👷 Automatically installs required modules.

I figure it's easier and more convenient this way.
Updated readme to inform a bit more about required modules, too.

khinsider.py

@@ -3,6 +3,55 @@
 
 # A script to download full soundtracks from khinsider.
 
+# --- Install prerequisites---
+
+# (This section in `if __name__ == '__main__':` is entirely unrelated to the
+# rest of the module, and doesn't even run if the module isn't run by itself.)
+
+if __name__ == '__main__':
+    import imp # To check modules without importing them.
+
+    requiredModules = [
+        ['requests', 'requests'], # Some modules don't have the same pypi name as
+        ['bs4', 'beautifulsoup4']  # import name. Therefore, two entries per module.
+    ]
+
+    def moduleExists(module):
+        try:
+            imp.find_module(module[0])
+        except ImportError:
+            return False
+        return True
+    def neededInstalls(requiredModules=requiredModules):
+        uninstalledModules = []
+        for module in requiredModules:
+            if not moduleExists(module):
+                uninstalledModules.append(module)
+        return uninstalledModules
+
+    def install(package):
+        pip.main(['install', '--quiet', package])
+    def installModules(modules, verbose=True):
+        for module in modules:
+            if verbose:
+                print "Installing " + module[1] + "..."
+            install(module[1])
+    def installRequiredModules(needed=None, verbose=True):
+        needed = neededInstalls() if needed is None else needed
+        installModules(neededInstalls(), verbose)
+
+    needed = neededInstalls()
+    if needed: # Only import pip if modules are actually missing.
+        try:
+            import pip # To install modules if they're not there.
+        except ImportError:
+            print "You don't seem to have pip installed!"
+            print "Get it from https://pip.readthedocs.org/en/latest/installing.html"
+
+    installRequiredModules(needed)
+
+# ------
+
 import requests
 from bs4 import BeautifulSoup
 

readme.md

@@ -18,9 +18,15 @@ Carefully put together by [@obskyr](http://twitter.com/obskyr)!
 ## Usage
 Just run `khinsider.py` from the command line with the sole parameter being the soundtrack you want to download. Easy!
 
-You're going to need [Python 2](https://www.python.org/downloads/), so install that (and [add it to your path](http://superuser.com/a/143121)) if you haven't already. Download for `khinsider.py` is on the right of this GitHub page - click "Download ZIP"!
+You're going to need [Python 2](https://www.python.org/downloads/), so install that (and [add it to your path](http://superuser.com/a/143121)) if you haven't already.
+
+You will also need to have [pip](https://pip.readthedocs.org/en/latest/installing.html) installed (download `get-pip.py` and run it) if you don't already have [requests](https://pypi.python.org/pypi/requests) and [Beautiful Soup 4](https://pypi.python.org/pypi/beautifulsoup4). The first time `khinsider.py` runs, it will install these two for you.
+
+Download for `khinsider.py` is on the right of this GitHub page - click "Download ZIP"!
 
 ## As a module
+`khinsider.py` requires two non-standard modules: [requests](https://pypi.python.org/pypi/requests) and [beautifulsoup4](https://pypi.python.org/pypi/beautifulsoup4). Just run a `pip install` on them (with [pip](https://pip.readthedocs.org/en/latest/installing.html)), or just run `khinsider.py` on its own once and it'll install them for you.
+
 Here are the functions you will be using:
 
 ###`khinsider.download(soundtrackName[, path="", verbose=False])`