Opa installation fails on Ubuntu with nodejs v0.10.0

Using the .run script as on 32bit Ubuntu 12.04.

On first run, Opa  correctly adds the nodejs PPA and attempts to both the nodejs and npm packages. Nodejs now includes npm, so the attempt to install npm uses the version from the ubuntu default repositories. This conflicts with the new nodejs package.

Attached pull request removes npm package installation. I'm afraid I don't know whether Opa will actually run against v0.10.0; if not, an alternative ppa will need to be set up.

```bash
$ opa create foo
node.js is missing, Download and install it ? (no will abort) [Yn] y
Reading package lists... Done
Building dependency tree       
Reading state information... Done
python-software-properties is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
You are about to add the following PPA to your system:
 Evented I/O for V8 javascript. Nodes goal is to provide an easy way to build scalable network programs
 More info: https://launchpad.net/~chris-lea/+archive/node.js
Press [ENTER] to continue or ctrl-c to cancel adding it
--SNIP---
Fetched 4,240 B in 5s (715 B/s)
Reading package lists... Done
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 nodejs : Conflicts: npm
E: Unable to correct problems, you have held broken packages.

$ sudo apt-cache show nodejs
Package: nodejs
Priority: extra
Section: web
Installed-Size: 14641
Maintainer: Jérémy Lal <kapouer@melix.org>
Architecture: i386
Version: 0.10.0-2chl1~precise1
Replaces: nodejs-dev (<= 0.8.22), npm (<= 1.2.14)
Provides: nodejs-dev, npm
Depends: libc6 (>= 2.15), libgcc1 (>= 1:4.1.1), libstdc++6 (>= 4.1.1), rlwrap
Conflicts: nodejs-dev, npm
Filename: pool/main/n/nodejs/nodejs_0.10.0-2chl1~precise1_i386.deb
Size: 5257880
MD5sum: 03ba3e94270431e9c210bfed74a9c712
SHA1: f623f21d810b0c772be2d4f14b7a029facd2f1c6
Description-en: Node.js event-based server-side javascript engine
 Node.js is similar in design to and influenced by systems like
 Ruby's Event Machine or Python's Twisted.
 .
 It takes the event model a bit further - it presents the event
 loop as a language construct instead of as a library.
 .
 Node.js is bundled with several useful libraries to handle server tasks :
 System, Events, Standard I/O, Modules, Timers, Child Processes, POSIX,
 HTTP, Multipart Parsing, TCP, DNS, Assert, Path, URL, Query Strings.
```