Fixes #4472 - i18n support
shell - temporarily disable command completion

Command completion fails with exception on Ruby < 1.9. This is caused by
a function Readline.line_buffer which is missing on older Ruby
platforms. The function is crucial for our completion and the problem
will be complicated to fix. I'm disabling it until we find a better
solution.
docs - installation instructions moved on a separate page
docs - updated installation instructions
docs - i18n
Merge pull request #91 from tstrachota/i18n

Fixes #4472 - i18n support