support the last 10 releases of pants; use git tag to specify the pants version to load instead of sha
support the last 10 releases of pants; use git tag to specify the pants version to load instead of sha

@zundel mentioned to specify a policy regarding how far back the regression test should go, and I think 10 releases make sense which goes back about 2-3 months.

Testing Done:
https://travis-ci.org/pantsbuild/intellij-pants-plugin/builds/97117271

Bugs closed: 84

Reviewed at https://rbcommons.com/s/twitter/r/3255/

wisechengyi/intellij-pants-plugin,pantsbuild/intellij-pants-plugin,pantsbuild/intellij-pants-plugin,pantsbuild/intellij-pants-plugin,wisechengyi/intellij-pants-plugin,pantsbuild/intellij-pants-plugin,wisechengyi/intellij-pants-plugin,pantsbuild/intellij-pants-plugin,wisechengyi/intellij-pants-plugin