geom_histogram exception with xlim

[andibuwono]

Hi @has2k1

Opened this issue which i think similar to #22

in short this throw an error

(ggplot(diamonds)
  + aes('depth', fill='cut', color='cut')
  + geom_histogram(alpha=0.1)
  + xlim(55, 70))

and this ok

(ggplot(diamonds)
  + aes('depth', fill='cut', color='cut')
  + geom_histogram(alpha=0.1))

and this ok to

(ggplot(diamonds)
  + aes('depth', fill='cut', color='cut')
  + geom_bar(alpha=0.1)
  + xlim(55, 70))

thanks before