Checking the cppman page for keywords results in inconsistent answers.

[Resparing]

Checking the cppman page for certain keywords will result in a function, such as the page for an int, while other keywords will have their own pages, such as a double.

Steps to reproduce:

cppman double
cppman int

[aitjcize]

This was because cppman will find the first match it encountered. The int keyword does not have a page matching the keyword, so the closest page was returned. I've modify the logic of query in the latest commit, now if a keyword results in multiple matches, a menu will be presented for selection, for example:

$ bin/cppman Lambda
1. std::experimental::reflect::Lambda - std::experimental::reflect::Lambda
2. std::experimental::reflect::LambdaCapture - std::experimental::reflect::LambdaCapture
3. experimental::reflect::Lambda - std::experimental::reflect::Lambda
4. experimental::reflect::LambdaCapture - std::experimental::reflect::LambdaCapture
5. Lambda expressions(since C++11) - Lambda expressions (since C++11)

Please enter the selection: