Make colours configurable by the calling code

Add in some more customization options
add bisect function

distanceFromIntersectArea wasn't working in some cases (see
https://github.com/benfred/venn.js/issues/3).

The problem was caused by using an unconstrained function minimizer to compute
this distance - which went awry when the solution was near one of the
constraints (i.e completely overlapped or completely disjoint).

Changed to compute this using bisection
fix
2 more examples from original blog post
Merge pull request #5 from benfred/add_bisect

Add bisect function
Merge branch 'customizable-colors' of github.com:AdamFerguson/venn.js
Merge pull request #2 from AdamFerguson/customizable-colors

Make colours configurable by the calling code
Merge branch 'master' of github.com:benfred/venn.js
pass style params to drawD3Diagram instead
remove border
bug fix for completely overlapped circles

this fixes issue #8
add tooltip example

This is an alternative to https://github.com/benfred/venn.js/pull/6 .
Fixed typos/misspellings in comments.
Fixed mistaken spelling correction for 'aesthetics'.
Show the object using JSON when there is an exception thrown.
Vertically center the text.
Center diagram within the SVG; as defined by width, height, and padding.
Merging my various branches back into master.
Merging my branches back into master.
Merged all of my branches back into my master.