Always return mimetype as string

[mohangk]

Currently MultiMime.lookup returns either
::MIME::Type if it uses MIME::Types or ::Mime::Type
and returns a string containing the content type
if it uses ::Rack::Mime. This change makes the
return type consistently a string, which is AFAICT
supported by all fog-providers.

This change also allows us to remove the unnecessary
type checking of the content-type in storage.rb as
we can be assured its a string. Something similar will need to
be done to support the JSON storage API with fog-google
so this is prep work

Tests still pass and have always been testing for strings anyway

[TravisBuddy]

Hey @mohangk,
Something went wrong with the build.

TravisCI finished with status errored, which means the build failed because of something unrelated to the tests, such as a problem with a dependency or the build process itself.

View build log

TravisBuddy Request Identifier: c55c6e40-3965-11e9-8b5a-7f317ad24fc3

[coveralls]

Pull Request Test Coverage Report for Build 306

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 60.6%

---

Totals
Change from base Build 305:	0.04%
Covered Lines:	323
Relevant Lines:	533

---

💛 - Coveralls

[TravisBuddy]

Hey @mohangk,
Something went wrong with the build.

TravisCI finished with status errored, which means the build failed because of something unrelated to the tests, such as a problem with a dependency or the build process itself.

View build log

TravisBuddy Request Identifier: 0f047ab0-3966-11e9-8b5a-7f317ad24fc3

[TravisBuddy]

Hey @mohangk,
Something went wrong with the build.

TravisCI finished with status errored, which means the build failed because of something unrelated to the tests, such as a problem with a dependency or the build process itself.

View build log

TravisBuddy Request Identifier: fadee5b0-3966-11e9-8b5a-7f317ad24fc3

[PikachuEXE]

Thanks for your PR
Can you rebase against master where the Travis build is fixed?

[mohangk]

Sorry I just realised you have fixed the build. Will rebase now. Apologies.

[PikachuEXE]

Ya this bundler version thing is failing travis build for many rails related projects...