Replace nil values with empty strings

[manuelmeurer]

As discussed in #402

[databyte]

Overall it looks good but it has to support 1.8.7.

Specifically each_with_object doesn't exist in 1.8.7 so you have to rewrite that bit. Sucks, yeah.

ERROR
  Rabl::Builder #to_hash when nil values are replaced with empty strings asserts that an empty string is returned as the value => undefined method `each_with_object' for {:name=>nil}:Hash occured
    at /home/travis/build/nesquena/rabl/test/builder_test.rb:52
    at /home/travis/build/nesquena/rabl/lib/rabl/builder.rb:20:in `build'
    at /home/travis/build/nesquena/rabl/lib/rabl/builder.rb:163:in `cache_results'
    at /home/travis/build/nesquena/rabl/lib/rabl/builder.rb:21:in `build'
    at /home/travis/build/nesquena/rabl/lib/rabl/builder.rb:62:in `compile_hash'

[nesquena]

Yeah we can probably just replace each_with_object for inject right and then return the hash on the last line for 1.8.7 support.

[manuelmeurer]

Any plans to merge this in?

[nesquena]

Thanks!

[manuelmeurer]

Great! Could you release v0.8.4?

[nesquena]

Yep released!

[manuelmeurer]

Cheers!