Change maven-compiler-plugin source and target from 1.7 to 1.8

[davidxia]

Change maven-compiler-plugin source and target from 1.7 to 1.8

to prepare for Java 8.
JAR should still be compatible with JRE 1.7.

Set Travis CI JDK to oraclejdk8.

fixes #756

[mattnworb]

could you also add something to the changelog? I think it would be good to bump the version too, like to 8.14 or whatever.

[codecov-io]

Codecov Report

Merging #1081 into master will increase coverage by 2.78%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1081      +/-   ##
============================================
+ Coverage     67.08%   69.86%   +2.78%     
  Complexity      789      789              
============================================
  Files           178      178              
  Lines          3287     3786     +499     
  Branches        385      392       +7     
============================================
+ Hits           2205     2645     +440     
- Misses          917      972      +55     
- Partials        165      169       +4

[mattnworb]

I don’t think it’s conpletely necessary to do a full version bump, since there’s no code API change. 8.14 would make sense to me too.

[davidxia]

Ah that's true. I'm not using any java 8 language features yet. I'll change to 8.14 then.

[diemol]

Thanks for moving it to Java 8 @davidxia!