Skip network tests if machine isn't on a network

Adds a new `requires_network` decorator which should be used if the test
requires a connection to a network resource like TARPIT_HOST. Otherwise, the
unit tests fail when running on an isolated machine.
Merge pull request #325 from kevinburke/network-unreachable

Skip network tests if machine isn't on a network
Minor typo on docs landing page
Merge pull request #327 from tahia-khan/master

Fixing minor typo on docs landing page
add HTTPHeaderDict
gratuitous tests for no reason
remove unused imports
add test that highlights httplib bug
Merge pull request #329 from jschneier/case-multi-headers

add HTTPHeaderDict
CHANGES for #329.
Use the platform-specific CA certificate locations if none provided
as per PEP-449 mirrors are deprecated
Add myself to contributors
Merge pull request #332 from ticosax/platform-ca-location

Platform ca location
CHANGES for #332
document and change HTTPHeaderDict, update CHANGES for bugfix
Merge pull request #333 from jschneier/master

document HTTPHeaderDict, update CHANGES for bugfix.
Formatting.
httpbin.org is just the right tool for this.
Merge pull request #334 from ticosax/swtich-to-httpbin.org

httpbin.org is just the right tool for this.