Added Travis-ci support
Updated build script to merge the branch with master on release
Fixing travis issue for the gemfile
Added travis gemfile
Updated gemfile again.
Prevent a type error when generating context with some Node types.

Certain Node types (Call, Lvalue, etc.) appear to have nested arrays
of tokens, instead of a single array. Producing context for one of
these Node subclasses would end up causing a crash, when 'region' is
called on an Array. Example:

  tree = Nasl::Parser.new.parse("if(description){exit.foo();}")
  exit_call = tree.all(:Call).first
  if_stmt   = tree.all(:If).first
  puts exit_call.context(if_stmt)

I am uncertain if the nested arrays of tokens are due to a grammar
inconsistency or something else, so I'm not sure if this is the right
place to fix it. That said, it does prevent the crash.
Prevent two Call nodes from being instantiated per Repetition.

The 'call_exp' rules do the Call node instantiation. The Repetition
rules do not have to take care of it.
Merge branch '0.1.2' into 0.2.0
Version bump to 0.2.0