Refactor Blanket::Wrapper#uri_from_parts to allow full paths

[nicooga]

This tiny refactor allows you to send full paths to the wrapper:

api = Blanket.wrap('https://api.github.com/')
=> #<Blanket::Wrapper:0x007fb04eeffd20
 @base_uri="https://api.github.com/",
 @extension=nil,
 @headers={},
 @params={},
 @uri_parts=[]>

api.get('users/inf0rmer/repos')
=> Response!

# or even/maybe, if you dont want to perform the request yet
api.send('users/inf0rmer/repos')
=> #<Blanket::Wrapper:0x007fb04a4fd3a8
 @base_uri="https://api.github.com/users/inf0rmer/repos",
 @extension=nil,
 @headers={},
 @params={},
 @uri_parts=[]>

[coveralls]

Coverage remained the same at 99.15% when pulling f04f008 on nicooga:feature/more_flexible_pathing into 78ecc7b on inf0rmer:master.

[inf0rmer]

Hi, thanks for contributing!

The code looks great, however would you mind complementing your PR with the following:

• A test case for the new functionality (so that we're sure future developments don't break the behaviour)
• Adding a small explanation of how the feature works to the README file

[nicooga]

There, docs and readme ready. And I also pushed the minor version number up to 2.0.1.

[coveralls]

Coverage increased (+0.01%) to 99.16% when pulling 6c1ae2a on nicooga:feature/more_flexible_pathing into 78ecc7b on inf0rmer:master.

[coveralls]

Coverage increased (+0.01%) to 99.16% when pulling f79e4e3 on nicooga:feature/more_flexible_pathing into 72226f0 on inf0rmer:master.

[coveralls]

Coverage increased (+0.01%) to 99.16% when pulling f79e4e3 on nicooga:feature/more_flexible_pathing into 72226f0 on inf0rmer:master.

[inf0rmer]

Thanks!