Merge pull request #27 from dmb2168/master

Updating Chris/Kira with Master
working on tree empty el problem
changing c_output tests to full tests
reverted last commit; still should have NULL preemptive
added new test for trees, moved bad tests to c output folder
rm string_lit from ir,output. renamed test9
Merge pull request #28 from dmb2168/master

Updating Chris/Kira with Master
lrxlib fixed segfault on tree comparison; gotta catch those rascal NULL trees
chris says sleep deprivation is the same as drinking too much; it's bad for the brain. took out destroy_tree within lrx_assign_tree_direct because it was going crazy. tree child operators seem to be working
fixed tests, took testing print statements out of lrxlib
added back test-full9.out went missing
Merge pull request #29 from dmb2168/chris_kira_semantic_analysis

Working on tree assignment and child operator