Add support for boolean operator

[ianjennings]

During development I found that "true" and "false" are always converted into strings, leaving no ability to compare against booleans.

This patch adds support for bools through the : operator.

EX:

?param=:true 

[Starefossen]

Thanks for the pull request @ianjennings and sorry for the late response!

I am tempted to propose that this should be done by default? We already parses numbers, I think that "true" and "false" string values should be parsed to true and false boolean values by default. What do you think?

[ianjennings]

From a usability standpoint, that's what I expected from the library. It wasn't until I echo'd the generated query that I saw bool values interpreted as a string.

👍 I vote to parse booleans by default.

[Starefossen]

Boolean parsing has been implemented by #11 and released in v2.0.0 🚀