add clearm support
* AUTHORS: updating list of contributors
* Rakefile: adding gem authors metadata, now mandatory
* ext/augeas/extconf.rb: add libxml2 headers and library to Makefile
* ruby-augeas.spec: add build req on libxml2-devel
Expose aug_srun as Augeas#srun

  * ext/augeas/_augeas.c: add Augeas#srun
  * ext/augeas/_augeas.h: split out header, add memstream utils from Augeas
  * tests/tc_augeas.rb: added test case for 'srun'
* .gitignore: ignore build files
Expose changes in Augeas 1.0.0 release

  * ext/augeas/_augeas.c: add Augeas#label, Augeas#rename, Augeas#text_retrieve
    and Augeas#text_store
  * lib/augeas.rb: add ".lns" suffix if a module name is passed to
    Augeas#transform to match aug_transform behaviour;
    add Augeas#clearm, #touch to mirror aug_srun commands;
    add Augeas#context= and #context to access /augeas/context
Add Travis CI settings
* Rakefile: replace deprecated rdoc/gem rake tasks
Add rake/rdoc dependencies for rake tasks, enable Ruby 2 tests
Prepare NEWS, AUTHORS and Rakefile for 0.5.0
* NEWS: correct date for 0.5.0 release
Make it work on OS X