Remove dependency on Java

While `unzip` has problems with extracting certain zip files[1], `7z`
does properly handle this test file. There is no reason to stick to
`jar` now.

Fixes #101.

 [1]: http://www.openipcam.com/files/Firmware/Foscam/FI8908W-fw11.14.1.46.zip

INSTALL.md

@@ -56,7 +56,7 @@ Binwalk relies on multiple external utilties in order to automatically extract/d
 
 ```bash
 # Install standard extraction utilities
-$ sudo apt-get install mtd-utils gzip bzip2 tar arj lhasa p7zip p7zip-full cabextract openjdk-6-jdk cramfsprogs cramfsswap squashfs-tools
+$ sudo apt-get install mtd-utils gzip bzip2 tar arj lhasa p7zip p7zip-full cabextract cramfsprogs cramfsswap squashfs-tools
 ```
 
 ```bash

src/binwalk/config/extract.conf

@@ -29,7 +29,7 @@
 ^xz compressed data:tar:tar xJf '%e'
 ^bzip2 compressed data:bz2:bzip2 -d -f '%e'
 ^compress'd data:Z:gzip -d '%e'
-^zip archive data:zip:jar xf '%e' # jar does a better job of unzipping than unzip does...
+^zip archive data:zip:7z x -y '%e':0,1
 ^posix tar archive:tar:tar xvf '%e'
 ^rar archive data:rar:unrar e '%e'
 ^rar archive data:rar:unrar -x '%e' # This is for the 'free' version