Add support for config files

This makes it more convenient to use a non-default basedir, for
example.

README.rst

@@ -61,12 +61,29 @@ Show help::
 
     $ multipy -h
 
+Here's a list of supported command line options::
+
+    -b BASEDIR   The base directory [default: ~/multipy]
+    -k           Keep temporary files and logs after installation
+    -n           Don't install distribute
+
+Upon startup, multipy tries to source ``~/.multipyrc`` and
+``~/.config/multipyrc``. The following variables can be assigned in
+these files::
+
+    Assignment...     has the same effect as:
+
+    basedir=BASEDIR   -b BASEDIR
+    keep_tmp=1        -k
+    no_distribute=1   -n
+
 
 Under the hood
 ==============
 
 By default, the top directory of the multipy is
-``basedir=$HOME/multipy``. This can be changed with the ``-b`` option.
+``basedir=$HOME/multipy``. This can be changed with the ``-b`` option
+or in the config files discussed in the last section.
 
 When Python X.Y is installed, the following things happen:
 

multipy

@@ -355,13 +355,22 @@ Commands:
         This is meant to be used to easily source the activate script
         in the shell:
 
-            . $(multipy activate 2.6)
+            . \$(multipy activate 2.6)
 
 Options:
     -b BASEDIR   The base directory [default: ~/multipy]
     -k           Keep temporary files and logs after installation
     -n           Don't install distribute
 
+Upon startup, ~/.multipyrc and ~/.config/multipyrc are loaded. The
+following variables can be assigned in these files:
+
+    Assignment...     has the same effect as:
+
+    basedir=BASEDIR   -b BASEDIR
+    keep_tmp=1        -k
+    no_distribute=1   -n
+
 Copyright (C) 2011 Petri Lehtinen. Licenced under the MIT license.
 
 EOF
@@ -372,6 +381,11 @@ basedir=$HOME/multipy
 no_distribute=0
 keep_tmp=0
 
+# Load config files
+: ${XDG_CONFIG_HOME:=$HOME/.config}
+[ -f $HOME/.multipyrc ] && . $HOME/.multipyrc
+[ -f $XDG_CONFIG_HOME/multipyrc ] && . $XDG_CONFIG_HOME/multipyrc
+
 while getopts "b:kn" opt; do
     case $opt in
         b)