Hardcoded dex2jar version

[Mr-TWX]

Hi @ajitsing , thanks for this Gem

Issue

I've tried to run it on MacOs and found and received the following error

user@MacBook-Pro-di-User ~ % apkToJava /Users/myuser/Desktop/base.apk
Initializing setup!!
checking for curl... yes
Installing dex2jar..
Warning: dex2jar 2.1 is already installed and up-to-date.
To reinstall 2.1, run:
  brew reinstall dex2jar
Done!
Setup done :)
Converting to dex..
Done!
Converting dex to jar..
/Users/myuser/.gem/ruby/2.6.0/gems/apkToJava-1.3.1/lib/apk_to_java.rb:53:in ``': No such file or directory - /usr/local/Cellar/dex2jar/2.0/bin/d2j-dex2jar (Errno::ENOENT)
	from /Users/myuser/.gem/ruby/2.6.0/gems/apkToJava-1.3.1/lib/apk_to_java.rb:53:in `create_jar'
	from /Users/myuser/.gem/ruby/2.6.0/gems/apkToJava-1.3.1/lib/apk_to_java.rb:82:in `dex_to_jar'
	from /Users/myuser/.gem/ruby/2.6.0/gems/apkToJava-1.3.1/lib/apk_to_java.rb:88:in `view_as_java_code'
	from /Users/myuser/.gem/ruby/2.6.0/gems/apkToJava-1.3.1/bin/apkToJava:61:in `execute'
	from /Users/myuser/.gem/ruby/2.6.0/gems/apkToJava-1.3.1/bin/apkToJava:65:in `<top (required)>'
	from /Users/myuser/gems/bin/apkToJava:23:in `load'
	from /Users/myuser/gems/bin/apkToJava:23:in `<main>'

Cause

Looking at the source code for mac_setup.rb, the DEX_TO_JARconstant is hardcoded to the 2.0 version.

Since the latest version available is 2.1, the error above is thrown.

Possible solutions

At the moment, I've managed to fix the issue by changing the mac_setup.rb file by updating the hardcoded reference from 2.0 to 2.1.

It would be nicer to have the apkToJava to automatically use the latest version of dex2jar