I am getting pretty desperate, i have tried every answer on the subject but nothing seems to work. 

the error log looks like this:

```
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby -r ./siteconf20150523-16458-46bzoo.rb extconf.rb --with-pg-config=/Applications/Postgres.app/Contents/Versions/9.3/bin/pg_config
Using config values from /Applications/Postgres.app/Contents/Versions/9.3/bin/pg_config
sh: /Applications/Postgres.app/Contents/Versions/9.3/bin/pg_config: No such file or directory
sh: /Applications/Postgres.app/Contents/Versions/9.3/bin/pg_config: No such file or directory
checking for libpq-fe.h... yes
checking for libpq/libpq-fs.h... yes
checking for pg_config_manual.h... yes
checking for PQconnectdb() in -lpq... no
checking for PQconnectdb() in -llibpq... no
checking for PQconnectdb() in -lms/libpq... no
Can't find the PostgreSQL client library (libpq)
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
    --with-pg
    --without-pg
    --enable-windows-cross
    --disable-windows-cross
    --with-pg-config
    --with-pg-dir
    --without-pg-dir
    --with-pg-include
    --without-pg-include=${pg-dir}/include
    --with-pg-lib
    --without-pg-lib=${pg-dir}/
    --with-pqlib
    --without-pqlib
    --with-libpqlib
    --without-libpqlib
    --with-ms/libpqlib
    --without-ms/libpqlib

extconf failed, exit code 1

Gem files will remain installed in /Users/kevinegstorf/.rvm/gems/ruby-2.0.0-p643/gems/pg-0.18.2 for inspection.
Results logged to /Users/kevinegstorf/.rvm/gems/ruby-2.0.0-p643/extensions/universal-darwin-14/2.0.0/pg-0.18.2/gem_make.out
An error occurred while installing pg (0.18.2), and Bundler cannot continue.
Make sure that `gem install pg -v '0.18.2'` succeeds before bundling.

```

Installing gem install pg -v '0.18.2' gives me back the same error
I hope someone can help me. tnx