'multialign' is a text property in mpl when *newlines* are present.

multiple-line annotations will now be tracekd properly in Plotly
updated annotations test to include new plotly 'align' parameter
mpl defaults text alignment to horizontal alignment when unspecified.
updated tests for new text alignment defaults.
Merge pull request #53 from plotly/issue-49

'multialign' is a text property in mpl when *newlines* are present.