Update INSTALL wrt missing dependencies

This patch updates the quick installation guide with
with respect to some missing dependencies. Besides,
it rephrases some instructions to make them more clear.
Signed-off-by: Helga Velroyen <helgav@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>

INSTALL

@@ -74,7 +74,8 @@ If bitarray is missing it can be installed from easy-install::
 
   $ easy_install bitarray
 
-Note that this does not install optional packages::
+Note that the previous instructions don't install optional packages.
+To install the optional package, run the following line.::
 
   $ apt-get install python-paramiko python-affinity qemu-utils
 
@@ -170,7 +171,8 @@ Some of these are also available as package in Debian/Ubuntu::
                     libghc-crypto-dev libghc-text-dev \
                     libghc-hinotify-dev libghc-regex-pcre-dev \
                     libpcre3-dev \
-                    libghc-attoparsec-dev libghc-vector-dev
+                    libghc-attoparsec-dev libghc-vector-dev \
+                    libghc6-zlib-dev
 
 Or in older versions of these distributions (using GHC 6.x)::
 
@@ -203,7 +205,7 @@ ones not available in your distribution packages) via ``cabal``::
 
   $ cabal install json network parallel utf8-string curl hslogger \
                   Crypto text hinotify==0.3.2 regex-pcre \
-                  attoparsec vector
+                  attoparsec vector base64-bytestring
 
 Haskell optional features
 ~~~~~~~~~~~~~~~~~~~~~~~~~