Fix build dependencies

So, current state of plugin emits a bunch of errors on "Connecting.." stage:

Resolving dependencies...
Configuring light-haskell-0.2.6...
cabal: At least the following dependencies are missing:
aeson ==0.7.*,
base ==4.6.*,
ghc-mod ==3.1.*,
network ==2.4.*,
process ==1.1.*,
stylish-haskell ==0.5.*,
text ==1.1.*

My configs:
MAC OS X 10.9.4
The Glorious Glasgow Haskell Compilation System, version 7.8.2
cabal-install version 1.20.0.3

I'm definitely not a specialist in either haskell or light table but it seems to solve issue :)