Added Javadoc plugin along with pre and post tags

Added the Maven Javadoc plugin to the pom file. Also added the Javadoc
tags pre and post for specifying pre- and postconditions.
Updated developers section in POM file.
Merge remote-tracking branch 'origin/dev' into javadoc
Merge branch 'dev' of https://github.com/CIRDLES/topsoil into dev
Merge branch 'dev' into javadoc
Merge branch 'dev' into Testing
Added tests for Vector2D
Removed Unused Imports and added param tag
Merge remote-tracking branch 'origin/javadoc' into Testing
Added Tests for the ConstantFunction
Added Tests for ParametricCurve3D
Deleted unused Imports from  ParametricCurve3D
Added Tests for the  ParametricCurve2D
Added tests for CubicBezierCurve
Merge pull request #72 from nityasantoshi/dev

Added JUnit tests and javadocs