Warnings from gem builded

[Loriowar]

Fix warnings from gem build action:

WARNING:  open-ended dependency on railties (>= 3.1) is not recommended
  if railties is semantically versioned, use:
    add_runtime_dependency 'railties', '~> 3.1'
WARNING:  open-ended dependency on select2-rails (>= 0) is not recommended
  if select2-rails is semantically versioned, use:
    add_runtime_dependency 'select2-rails', '~> 0'
WARNING:  open-ended dependency on coffee-rails (>= 0) is not recommended
  if coffee-rails is semantically versioned, use:
    add_runtime_dependency 'coffee-rails', '~> 0'
WARNING:  open-ended dependency on rake (>= 0, development) is not recommended
  if rake is semantically versioned, use:
    add_development_dependency 'rake', '~> 0'
WARNING:  pessimistic dependency on rails (~> 3.2.12, development) may be overly strict
  if rails is semantically versioned, use:
    add_development_dependency 'rails', '~> 3.2', '>= 3.2.12'
WARNING:  See http://guides.rubygems.org/specification-reference/ for help