removed typo by replacing `obseve()` with `observe()`, fixing issue #914#915

itziakos merged 2 commits intoenthought:mainenthought/chaco:mainfrom

markasbach:fix/914_typo_in_base_2d_plot_pymarkasbach/chaco:fix/914_typo_in_base_2d_plot_pyCopy head branch name to clipboard