Fix URL and Example

[biomunky]

• fix the default url, was always pointing at sources - no added tests!
• add an example to fetch articles for a given query in the last ten days

[lotia]

GIMMEH FIXIZ. WE CAN HAZ COMYLASHUN ERURZ. DEETAYLES BILOUW

   Compiling newsapi v0.1.0 (/Users/lotia/development/rust/newsapi)
error[E0061]: this function takes 2 parameters but 1 parameter was supplied
   --> src/newsapi/api.rs:293:23
    |
82  |     fn build_url(&self, base_url: &str, allowed_params: Vec<&str>) -> String {
    |     ------------------------------------------------------------------------ defined here
...
293 |         let url = api.build_url(allowed_params);
    |                       ^^^^^^^^^ expected 2 parameters

error[E0308]: mismatched types
   --> src/newsapi/api.rs:349:16
    |
349 |         api.to(to).from(from);
    |                ^^
    |                |
    |                expected reference, found struct `chrono::datetime::DateTime`
    |                help: consider borrowing here: `&to`
    |
    = note: expected type `&chrono::datetime::DateTime<chrono::offset::utc::Utc>`
               found type `chrono::datetime::DateTime<chrono::offset::utc::Utc>`

error[E0308]: mismatched types
   --> src/newsapi/api.rs:349:25
    |
349 |         api.to(to).from(from);
    |                         ^^^^
    |                         |
    |                         expected reference, found struct `chrono::datetime::DateTime`
    |                         help: consider borrowing here: `&from`
    |
    = note: expected type `&chrono::datetime::DateTime<chrono::offset::utc::Utc>`
               found type `chrono::datetime::DateTime<chrono::offset::utc::Utc>`

error: aborting due to 3 previous errors

Some errors occurred: E0061, E0308.
For more information about an error, try `rustc --explain E0061`.
error: Could not compile `newsapi`.
warning: build failed, waiting for other jobs to finish...
error: build failed

[biomunky]

tired enough to forget changing the unit tests!