Add initial version of the library
General improvements all over

- Take advantage of bashisms for cleaner and more robust code
- Make variables readonly wherever applicable
- Fix some keychain-related bugs; make it optional
- Show function name in warning/error messages
Demonstrate bootstrapping technique in README
Various changes in the API and function behavior

- Bumped IBL_VERSION to 0.3.0
- Add the ff. utility functions for working with provisioning profiles:
  * ibl_get_profile_uuid
  * ibl_install_profile
- IBL_BUILD_CONF is now exported in ibl_init instead of ibl_build
- ibl_build no longer saves the build output to $IBL_BUILD_DIR/xcodebuild.log
- ibl_archive_dsym now prints the zipped dSYM's filename to stdout
- Rename ibl_package to ibl_package_ipa
- ibl_package_ipa now prints the IPA filename to stdout
- ibl_package_ipa now accepts three parameters in the ff. order:
  1. suffix (no suffix by default)
  2. provisioning profile (defaults to PROVISIONING_PROFILE)
  3. code sign identity (defaults to CODE_SIGN_IDENTITY)
Update docs for 0.3.0