error message when rehash fails on non-writable directory

Fixes #238
tests galore
configure Travis
skip Ruby stuff on Travis
use C on Travis for even less overhead
add hook lookup tests
fix resolving symlinks in rbenv-hooks
Don't duplicate shims in PATH
tests for rbenv-init
replace tab with spaces
Merge pull request #367 from shoyan/master

replace tab with spaces
fix iterating through paths that have spaces in them

Fixes #344, #196
add tests for exec
fix exec fails for invalid version
hack around the hack around bash `echo`
test completions for exec
add tests for completions
improve detection of completion support for commands

Enable JavasCript, Lua and Erlang scripts to provide completions
saner assertions for multiline output
simplify iterating through arglist