Merge pull request #17 from pepijnkokke/master

Adding `DecStrictPartialOrder` to Relation.Binary
 [ agda-lib-ffi ] Fixed compilation with GHC 7.8.2.
Add implicit Level argument to isInj_1 and isInj_2
Merge pull request #18 from aztek/master

Make Data.Sum.isInj_1 and Data.Sum.isInj_2 level-polymorphic
Updated the copyright year range.
Included Evgeny Kotelnikov in the list of contributors.
Included James Chapman in the list of contributors.
Fixed whitespace issues.
Preparation for the release of version 0.8.
Removed release-specific information.
Included Pepijn Kokke in the list of contributors.
Added .mailmap file.

The information from some Git commands, e.g. git shortlog -nse, is
better by using this file.
Added two simple properties stating that dropping or taking with the length results in the empty/input list respectively.