Added LiveScript to source install steps

Without LiveScript installed, the following occurs during the install of plv8x:

```
$ npm i -g .

> plv8x@0.6.5 prepublish .
> env PATH="./node_modules/.bin:$PATH" lsc -cj package.ls &&
env PATH="./node_modules/.bin:$PATH" lsc -bpc bin/cmd.ls > bin/cmd.js &&
env PATH="./node_modules/.bin:$PATH" lsc -bc -o lib src

env: lsc: No such file or directory
npm ERR! addLocalDirectory Could not pack "." to "/var/lib/postgresql/.npm/plv8x/0.6.5/package.tgz"
npm ERR! addLocal Could not install .
npm ERR! plv8x@0.6.5 prepublish: `env PATH="./node_modules/.bin:$PATH" lsc -cj package.ls &&
npm ERR! env PATH="./node_modules/.bin:$PATH" lsc -bpc bin/cmd.ls > bin/cmd.js &&
npm ERR! env PATH="./node_modules/.bin:$PATH" lsc -bc -o lib src`
npm ERR! Exit status 127
npm ERR! 
npm ERR! Failed at the plv8x@0.6.5 prepublish script.
npm ERR! This is most likely a problem with the plv8x package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     env PATH="./node_modules/.bin:$PATH" lsc -cj package.ls &&
npm ERR! env PATH="./node_modules/.bin:$PATH" lsc -bpc bin/cmd.ls > bin/cmd.js &&
npm ERR! env PATH="./node_modules/.bin:$PATH" lsc -bc -o lib src
npm ERR! You can get their info via:
npm ERR!     npm owner ls plv8x
npm ERR! There is likely additional logging output above.

npm ERR! System Linux 3.13.0-30-generic
npm ERR! command "/var/lib/postgresql/.local/bin/node" "/var/lib/postgresql/.local/bin/npm" "i" "-g" "."
npm ERR! cwd /var/lib/postgresql/src/plv8x
npm ERR! node -v v0.10.29
npm ERR! npm -v 1.4.14
npm ERR! code ELIFECYCLE
npm ERR! 
npm ERR! Additional logging details can be found in:
npm ERR!     /var/lib/postgresql/src/plv8x/npm-debug.log
npm ERR! not ok code 0
```
After installing LiveScript, the installation of plv8x completes successfully:

```
$ npm install -g LiveScript
/var/lib/postgresql/.local/bin/livescript -> /var/lib/postgresql/.local/lib/node_modules/LiveScript/bin/livescript
/var/lib/postgresql/.local/bin/lsc -> /var/lib/postgresql/.local/lib/node_modules/LiveScript/bin/lsc
/var/lib/postgresql/.local/bin/slake -> /var/lib/postgresql/.local/lib/node_modules/LiveScript/bin/slake
LiveScript@1.2.0 /var/lib/postgresql/.local/lib/node_modules/LiveScript

$ npm install -g .
 
> plv8x@0.6.5 prepublish .
> env PATH="./node_modules/.bin:$PATH" lsc -cj package.ls &&
env PATH="./node_modules/.bin:$PATH" lsc -bpc bin/cmd.ls > bin/cmd.js &&
env PATH="./node_modules/.bin:$PATH" lsc -bc -o lib src

 
> pg@2.8.5 install /var/lib/postgresql/.local/lib/node_modules/plv8x/node_modules/pg
> node-gyp rebuild || (exit 0)

make: Entering directory `/var/lib/postgresql/.local/lib/node_modules/plv8x/node_modules/pg/build'
  CXX(target) Release/obj.target/binding/src/binding.o
  SOLINK_MODULE(target) Release/obj.target/binding.node
  SOLINK_MODULE(target) Release/obj.target/binding.node: Finished
  COPY Release/binding.node
make: Leaving directory `/var/lib/postgresql/.local/lib/node_modules/plv8x/node_modules/pg/build'
/var/lib/postgresql/.local/bin/plv8x -> /var/lib/postgresql/.local/lib/node_modules/plv8x/bin/cmd.js
plv8x@0.6.5 /var/lib/postgresql/.local/lib/node_modules/plv8x
├── async@0.2.10
├── tmp@0.0.23
├── resolve@0.6.3
├── optimist@0.6.1 (wordwrap@0.0.2, minimist@0.0.10)
├── LiveScript@1.2.0 (prelude-ls@1.0.3)
├── js-yaml@3.0.2 (esprima@1.0.4, argparse@0.1.15)
├── one@2.5.2 (flatten-array@0.0.4, functools@1.4.0, boxcars@0.0.6, hogan.js@2.0.0, debug@1.0.2, glob@4.0.3)
└── pg@2.8.5 (buffer-writer@1.0.0, generic-pool@2.0.3, nan@0.6.0)
```